THE  UNIVERSITY 

OF  ILLINOIS 

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NATURAL  HISTORY  SURVEY 

5705 

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v.7cop.4 


ILLINOIS  BIOLOGICAL 
MONOGRAPHS 

Vol.  VII  April,  1922  No.  2 


Editorial  Committee 


Stephen  Alfred  Forbes  William  Trelease 

Henry  Baldwin  Ward 


Published  under  the 

Auspices  of  the  Graduate  School  by 

THE  University  of  Illinois  Press 


Copyright,  1922  by  the  Untvebstty  or  Illinois 
Distributed  August  5, 1922 


THE  MOLLUSCAN  FAUNA  OF  THE 

BIG  VERMILION  RIVER, 

ILLINOIS 

With  Special  Reference  to  its  Modification  as  the  Result  of 
Pollution  by  Sewage  and  Manufacturing  Wastes 


WITH  FIFTEEN  PLATES  AND  ELEVEN  TABLES 


BY 

FRANK  COLLINS  BAKER 

Curator  of  the  Museum  of  Natural  History 

University  of  Illinois 


Contributions  from  the 

Museum  of  Natural  History  of  the  University  of  Illinois 

No.  22 


TABLE  OF  CONTENTS 


Introduction 7 

Acknowledgments 8 

Physical  Features  of  the  Big  Vermilion  Basin 10 

General  Biology  of  the  Big  Vermilion  River 15 

Plants 15 

Worms 15 

Crustacea 16 

Aquatic  Insects .' 16 

Higher  Vertebrates 18 

Fish  Fauna  of  the  Big  Vermilion  River 18 

General  Distribution  of  the  Mollusk  Fauna 24 

Ecological  Variation 25 

Comparisons  with  Other  River  Systems 28 

Systematic  Discussion  of  the  Mollusca 31 

Unionidae 31 

Sphaeriidae 58 

Pleuroceridae 59 

Amnicolidae 60 

Viviparidae 61 

Ancylidae 63 

Physidae 64 

Planorbidae 64 

L)minaeidae 65 

Pollution  of  the  Salt  Fork  by  Sewage  and  Manufacturing  Wastes 67 

General  Nature  of  Stream  Pollution 67 

Sewage  Pollution  in  the  Salt  Fork 72 

Recent  Examination  of  the  Polluted  Portion  of  Salt  Fork 80 

Sununary  of  Salt  Fork  Conditions 88 

Summary  and  Conclusions 90 

Unfavorable  Influences 90 

Parasites  and  Pathologic  Agencies 91 

Economic  Considerations 91 

Bibliography 94 

Explanation  of  Plates 97 


lOSI  FA  UNA  OF  BIG  VERMIUON  RI VER—BA  KER 


INTRODUCTION 

The  present  paper  embodies  the  result  of  investigations  of  the  mollusk 
fauna  of  one  of  the  smaller  rivers  of  the  State  of  Illinois,  the  Big  Vermilion, 
carried  on  during  the  years  1918  to  1920.  To  this  are  added  notes  on 
another  river,  the  Sangamon,  for  comparison.  While  all  groups  of  mol- 
lusks  were  considered,  special  emphasis  has  been  placed  on  the  Unionidae 
or  pearly  fresh  water  mussels  (Naiades),  on  account  of  their  abundance, 
their  significance  in  matters  of  geographic  distribution,  and  their  impor- 
tance from  an  economic  standpoint,  as  raw  material  from  which  pearl 
buttons  are  made. 

For  a  number  of  years,  the  United  States  Bureau  of  Fisheries  has  been 
engaged  in  conducting  a  series  of  investigations  of  several  rivers  of  Illinois 
and  Indiana,  for  the  purpose  of  ascertaining  the  mussel  resources  of  these 
streams.  In  view  of  the  rapid  depletion  of  the  supply  in  the  larger  rivers 
(Mississippi,  Ohio,  Illinois)  it  becomes  necessary  to  search  the  smaller 
streams  to  replenish  the  older  beds.  The  Maumee  and  the  Kankakee 
(Wilson  and  Clark,  1912),  as  well  as  the  Illinois  (Danglade,  1914),  have 
recently  been  rather  carefully  surveyed  with  interesting  and  important 
results. 

It  was  thought  that  a  somewhat  similar  investigation  of  the  Big  Ver- 
milion River  would  be  of  value.  The  scope  of  the  investigation  included 
everything  that  appeared  to  affect  the  moUuscan  life  of  the  river,  physical 
characters,  pollution,  general  relation  and  number  of  species.  It  was 
believed,  also,  that  the  Big  Vermilion,  as  well  as  other  smaller  streams 
in  the  State,  might  provide  good  breeding  stock  with  which  to  carry  on 
artificial  glochidial  infection  of  fish,  and  the  results  seem  to  warrant  the 
assumption.  It  will  be  necessary  to  make  more  or  less  detailed  surveys  of 
all  of  the  smaller  rivers  and  their  tributaries,  and  the  present  paper  may 
be  considered  a  contribution  toward  this  end,  covering  fully  the  Big  Ver- 
milion from  its  upper  waters  to  the  vicinity  of  Danville,  a  distance  of  about 
forty-five  miles  by  stream.  A  portion  of  the  Sangamon  is  considered,  and 
this  river  may  also  prove  a  valuable  source  of  mussel  material. 

Little  has  been  done  by  field  naturalists  in  the  study  of  the  distribution 
of  the  molluscan  fauna  of  a  stream  from  the  headwaters  to  the  larger 
portions  of  these  rivers.  Perhaps  the  most  thorough  and  notable  study 
of  this  character  was  carried  on  by  Adams  (1900,  1915),  on  the  genus  lo 
in  which  the  Tennessee  River  and  its  tributaries  (Powell,  Clinch,  Holston, 
French  Broad,  Nolichucky,  etc.)  were  studied  from  sources  to  Chattanooga. 


8  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [106 

Ortmann  has  made  a  study  of  the  distribution  of  the  Naiades  in  the 
streams  of  Tennessee  from  this  standpoint,  using  material  collected  by 
Adams  (Ortmann,  1918);  and  Wilson  and  Clark  (1912)  have  added  greatly 
to  our  knowledge  of  the  comparative  distribution  of  the  mussel  faunas 
of  the  Kankakee  and  Maumee  rivers. 

Studies  of  this  kind  bring  out  thfe  fact  that  certain  species  are  charac- 
teristic of  the  upper  reaches  of  a  stream  while  others  are  found  only  in  the 
lower  part.  Barriers,  such  as  falls  and  polluted  water,  are  also  seen  to  have 
a  large  influence  on  the  distribution  of  mollusks,  especially  river  mussels. 
The  same  species  may  also  vary  in  size  or  shape  in  different  parts  of  the 
streafti,  as  noted  by  Ortmann  (1920).  In  fact,  a  true  picture  of  the  charac- 
teristics of  the  fauna  of  a  river  or  smaller  stream  can  be  gained  only  by  this 
method,  which  the  present  paper  clearly  shows. 

The  Salt  Fork  of  the  Big  Vermilion  is  a  striking  example  of  the  ill 
effect  of  sewage  and  other  pollution  on  the  fauna  of  a  stream.  It  was 
carefully  studied  from  this  standpoint  in  order  to  determine  accurately 
the  distance  that  the  polluted  stream  must  flow  before  a  normal  fauna  can 
establish  itself,  and  to  ascertain  the  relative  effect  of  pollution  on  different 
species  of  mussels  as  well  as  on  other  aquatic  animals.  Mussels  and  cray- 
fishes are  considered  good  indicators  of  the  measure  of  pollution  in  a  stream 
and  the  absence  of  both  of  these  groups  of  animals  from  the  upper  part  of 
the  Salt  Fork  is  ample  evidence  of  the  septic  condition  of  this  stream. 

The  work  was  largely  carried  on  during  the  months  of  August,  Septem- 
ber, and  October,  when  the  water  was  low.  Collecting  was  done  by  wading 
in  the  stream  as  deep  as  hip  rubber  boots  would  permit.  In  the  shallow 
water  (up  to  two  feet  in  depth)  the  entire  bottom  was  gone  over  with  the 
hands,  and  the  mussels  and  other  mollusks  thus  picked  from  the  bottom 
of  mud,  gravel,  and  sand.  Samples  of  all  mollusks,  j»s  well  as  associated 
animals  of  the  other  groups,  have  been  preserved  in  the  Natural  History 
Museum  of  the  University  of  Illinois. 

The  different  areas  of  the  region  studied  are  covered  by  three  maps  of 
the  United  States  Geological  Survey,  the  Mahomet,  Champaign,  and  Dan- 
ville Folios,  and  on  these  the  stations  recorded  in  this  paper  may  easily 
be  located. 

ACKNOWLEDGMENTS 

The  writer  is  greatly  indebted  to  Professor  Frank  Smith,  not  only  for 
invaluable  assistance  in  collecting  much  of  the  material  upon  which  the 
paper  is  based,  but  also  for  many  notes  on  the  distribution  of  the  Naiades 
and  other  mollusks  in  the  two  river  systems.  Professor  Smith  has  studied 
the  fauna  of  the  Salt  Fork  and  the  Sangamon  streams  for  many  years, 
collecting  from  them  at  different  times  of  the  year.  His  classes  in  zoology 
have  visited  Homer  Park  yearly  for  a  long  period  and  thus  the  mollusk 


107]  FA  UNA  OF  BIG  VERMIUON  RIVER— BAKER  9 

fauna  of  this  locality  is  better  known  than  that  of  any  other  part  of  the 
stream. 

To  Professor  Smith  the  writer  is  also  indebted  for  the  identification  of 
the  worms  and  crayfish,  and  the  determination  of  the  animal  life  in  the 
samples  of  bottom  sludge  from  the  polluted  part  of  Salt  Fork.  The  sincere 
thanks  of  the  writer  are  due  to  the  persons  noted  below;  the  group  of  ani- 
mals or  plants  which  they  have  identified  is  indicated:  Dr.  Charles  P. 
Alexander,  Coleoptera  and  other  insects;  Dr.  Edward  Bartow;  Dr.  Stephen 
A.  Forbes;  Mr.  Calvin  Goodrich,  Goniobasis;  Dr.  George  M.  Higgins;  Mr. 
John  Malloch,  Diptera;  Dr.  J.  Percy  Moore,  Hirudinea;  Professor  James  E. 
Smith;  Dr.  E.  N.  Transeau,  Algae;  Dr.  Victor  Sterki,  Sphaeriidae;  Dr. 
Harley  J.  Van  Cleave;  Dr.  Bryant  Walker,  Ancylidae  and  other  moUusks. 


10  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [108 


PHYSICAL  FEATURES  OF  THE  BIG  VERMILION  BASIN 

The  Big  Vermilion  River  drains  about  1,500  square  miles  in  Champaign, 
Ford,  and  Vermilion  counties  in  Illinois  and  a  small  portion  of  Warren  and  • 
Fountain  counties,  Indiana.  The  North  Fork  also  drains  from  a  small 
territory  in  the  southeastern  part  of  Iroquois  County,  Illinois.  The  main 
stream,  known  as  Middle  Fork,  rises  in  the  southern  part  of  Ford  County 
near  the  town  of  Melvin,  in  the  Bloomington  morainic  system,  at  a  height 
of  800  feet  above  sea  level.  Its  course  is  southeastward,  between  the  hills 
of  the  moraine  known  as  the  Roberts  and  Melvin  ridges,  passing  through 
the  latter  and  uniting  with  a  tributary  known  as  the  West  Branch  of  the 
Middle  Fork,  which  also  rises  at  an  elevation  of  800  feet  in  the  Roberts 
ridge.  At  Potomac,  the  stream  turns  southward,  cuts  through  the  outer 
ridge  of  the  Bloomington  moraine  and  crosses  the  plain  of  the  Champlain 
till  sheet,  uniting  with  the  Salt  Fork  about  six  miles  west  of  Danville. 

The  largest  western  tributary,  known  as  the  Salt  Fork,  rises  in  the  till 
plain  in  the  north-central  part  of  Champaign  County,  near  Thomasboro, 
at  an  elevation  of  about  740  feet  above  the  sea.  It  drains  the  till  plain 
lying  between  the  Bloomington  moraine  on  the  north  and  the  Champaign 
moraine  on  the  south.  It  flows  in  a  south  and  east  direction  for  about 
55  miles^  and  unites  with  the  Middle  Fork  as  described  above.  A  large 
tributary  of  Salt  Fork,  known  as  Spoon  River*  rises  in  the  northeastern 
part  of  Champaign  County,  in  two  branches,  not  far  from  the  outer  ridge 
of  the  Bloomington  moraine.  Its  general  course  is  southward  for  a  dis- 
tance of  about  ten  miles,  where  it  unites  with  the  Salt  Fork  near  St.  Joseph. 

Another  large  tributary  is  known  as  the  North  Fork,  which  rises  in  the 
southeastern  comer  of  Iroquois  County  in  the  inner  ridge  of  the  Blooming- 
ton moraine.  It  flows  southward,  cutting  through  the  middle  and  outer 
ridges  of  the  moraine,  crosses  a  part  of  the  Champaign  till  plain  and  unites 
with  the  Big  Vermilion  at  Danville.  This  tributary  has  a  length  of  about 
40  miles.  From  Danville  the  larger  stream  flows  southeastward  for  about 
20  mUes,  crossing  a  part  of  Vermilion  County,  Indiana,  and  empties  into 
the  Wabash  River  10  miles  from  the  Illinois  State  line. 

The  basin  of  the  Big  Vermilion  River  lies  in  or  is  surrounded  by  glacial 
moraines  of  the  Early  Wisconsin  glaciation,  the  Bloomington  moraine  on 

» Length  of  rivers  designates  total  length  including  all  meanders. 
'  Not  to  be  confounded  with  Spoon  River  entering  the  Illinois  River  near  Havana,  Mason 
County. 


109]  FAUNA  OP  BIG  VERMILION  RIVER— BAKER  li 

the  north  and  the  Champaign  moraine  on  the  south.  In  its  course  it  cuts 
through  the  Bloomington  moraine  in  several  places.  The  territory  drained 
includes  a  small  part  of  the  Bloomington  till  plain  and  a  considerable  part 
of  the  Champaign  till  plain  (Leverett,  Illinois  Glacial  Lobe,  plate  VI.) 
As  there  are  no  outcroppings  of  rock  in  this  area  the  streams  have  cut  well 
defined,  though  meandering,  channels.  The  upper,  small,  creek-like  tribu- 
taries have  sunk  their  beds  bat  a  few  feet  below  the  general  level  of  the 
country,  but  lower  down,  the  stream,  after  receiving  several  large  tributa- 
ries, has  cut  its  bed  to  a  depth  of  ten  or  fifteen  feet.  In  Middle  Fork  and 
North  Fork,  and  in  the  Big  Vermilion  from  above  Middle  Fork  to  the 
Wabash,  the  river  has  cut  deep  canyons  upwards  of  200  feet  in  depth, 
which  produce  some  of  the  most  picturesque  scenery  in  the  State  of  Illinois. 
This  river  valley  varies  from  half  a  mile  to  a  mile  in  width  and  in  one  place, 
about  four  miles  below  Danville,  it  widens  to  form  a  large  amphitheater 
two  miles  wide  and  a  mile  long,  with  cliflfs  and  hills  rising  on  all  sides  to  a 
height  of  over  150  feet. 

Outside  of  the  stream  valleys  the  country  is  a  flat  till  plain,  largely 
devoted  to  crop  purposes.  Ridges,  made  up  of  the  Champaign  and  Bloom- 
ington moraines  and  their  branches,  occur  and  have  been  largely  instru- 
mental in  directing  the  course  of  some  of  the  stream  drainage.  The  Salt 
Fork  turns  to  the  north  after  leaving  Urbana,  and  passes  around  Yankee 
ridge  (a  branch  of  the  Champaign  moraine)  near  the  Brownfield  woods, 
and  spurs  from  the  Champaign  moraine  occur  in  several  places  on  the  west 
and  south  banks  of  the  Salt  Fork,  which  are  relatively  high  and  the  stream 
skirts  their  bases. 

The  bottom  of  the  main  stream  and  its  tributaries  varies  greatly. 
The  small  tributaries  mostly  have  mud  bottoms.  In  Spoon  River  the 
bottom  is  of  mud  in  most  places  and  the  water  is  of  considerable  depth, 
even  in  summer  (three  to  four  feet  maximum  in  August).  In  places 
there  are  riffles  where  the  water  is  very  shallow  (a  foot  or  less)  and  the  bot- 
tom here  is  of  sand  and  fine  gravel.  The  Salt  Fork  below  St.  Joseph  is 
made  up  of  stretches  of  stream  where  riffles  with  sand  and  gravel  bottom 
alternate  with  deeper  back  water  with  mud  bottom.  Near  Muncie  there 
are  outcrops  of  rock,  a  smaU  tributary.  Stony  Creek,  flowing  over  a  stony 
bed.  In  the  Middle  Fork,  shale  rock  outcrops  in  several  places,  notably 
below  the  interurban  bridge,  where  the  whole  bottom  is  composed  of  a 
sheet  of  rock  with  a  thin  coating  of  sediment  in  spots.  The  same  conditions 
are  found  in  patts  of  the  North  Fork  and  in  the  Big  Vermilion.  These 
varying  conditions  provide  the  most  favorable  environment  for  the  growth 
of  river  mussels,  a  fact  made  evident  by  the  large  naiad  fauna  found  in 
the  stream  despite  the  unfavorable  effects  of  sewage  and  waste  pollution. 

Natural  dams  occur  in  a  few  places  in  the  Salt  Fork,  caused  by  the 
accumulation  of  debris  which  has  lodged  against  the  trunk  of  a  tree  that 


12  ILUNOIS  BIOLOGICAL  MONOGRAPHS  fllO 

has  fallen  across  the  stream.  At  Homer  Park,  an  artificial  dam  about  five 
feet  in  height  causes  slack  water  for  several  miles  up  the  stream.  This  dam 
markedly  afifects  the  mollusk  fauna,  the  tumbling  of  the  water  over  the 
dam  mixing  air  with  the  polluted  water  and  providing  the  dissolved  oxygen 
so  necessary  to  naiad  life.  It  is  probable  that  the  large  number  of  species 
of  mussels  found  at  some  stations  above  this  dam  is  due  largely  to  the 
presence  of  sections  of  the  stream  where  riffles  provide  the  oxygenating 
agent.  Mussels  were  usually  found  in  or  near  such  habitats.  The  mussel 
fauna  below  the  Homer  Park  dam  numbers  28  species  while  above  the  dam, 
as  far  up  stream  as  Sidney,  only  17  species  occur,  10  species  not  passing 
the  barrier,  although  the  environment  does  not  differ  essentially.  The 
current  in  the  river  is  rapid  over  the  riffles  but  rather  sluggish  in  the  deeper 
places.  The  difference  between  high  and  low  water  (spring  and  fall)  is 
about  six  feet.    The  streams  usually  vary  in  width  from  ten  to  thirty  feet. 

In  the  late  summer  and  fall  the  small  tributary  streams  (creeks  and 
rivulets)  flowing  into  Salt  Fork  and  other  branches  of  the  Big  Vermilion 
are  usually  either  dry  or  contain  scattered  pools  of  water  throughout  their 
length.  They  do  not  contribute  any  water,  therefore,  to  the  larger  stream 
at  this  time  of  the  year.  The  mollusks  living  in  these  tributaries  bury 
themselves  in  the  mud  during  this  period  of  dry  bottom  and  hibernate. 
Many  die  at  this  time. 

The  banks  of  the  stream  valleys,  exclusive  of  the  small  tributaries,  are 
for  the  most  part  high  and  well  wooded  especially  where  the  valley  floor 
is  wide  enough  to  permit  meandering,  in  which  cases  the  flat  floodplains 
are  abundantly  wooded.  These  flat  areas  vary  from  a  few  hundred  feet 
to  a  half  mile  in  width.  About  two  miles  above  Sidney  an  island  has  been 
formed  by  the  forking  of  the  stream,  the  area  embraced  being  about  650 
by  1200  feet.  At  this  place  the  right  bank  is  20  feet  high  and  the  left  bank 
quite  low.  The  presence  of  fossil  shells  indicates  that  the  island  was  prob- 
ably the  result  of  silt  accumulation  during  a  long  period  of  time.  The 
wooded  banks  of  the  stream  alternate  with  farm  lands,  some  in  pasture 
and  others  in  crops.  Many  of  the  crop  lands  have  a  fringe  of  timber  border- 
ing the  stream.  That  the  stream  is  high  and  powerful  during  the  spring 
when  it  is  in  flood  is  evidenced  by  the  tangled  mass  of  logs  and  other  woody 
debris  which  thickly  cover  the  flood  plain  areas  along  the  valley.  Such 
conditions  were  especially  noted  between  Sidney  and  Homer  Park. 

The  current  varies  somewhat,  being  relatively  sluggish  in  the  backwater 
above  dams  and  riffles,  but  quite  swift  over  the  shallow  places.  During  the 
flood  periods  of  spring  and  early  summer  the  current  is  quite  swift  and  in 
places  becomes  torrential.  This  condition  is  indicated  by  the  large  number 
of  trees  which  have  been  thrown  on  the  flood  plains  far  above  the  margin 
of  low  water.  As  measured  during  the  month  of  October  the  current  in 
the  Salt  Fork  at  Urbana  and  a  few  miles  down  the  stream  had  a  velocity 


Ill)  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  13 

of  from  half  a  mile  to  a  mile  an  hour.  The  water  was  very  low  when  these 
measurements  were  taken  by  the  State  Water  Survey.  In  its  course  of  90 
miles  to  the  Wabash  River,  the  Big  Vermilion  River  falls  about  320  feet  or 
3H  feet  per  mile.  It  thus  has  a  greater  fall  than  either  the  Kankakee, 
which  is  300  miles  long  and  has  a  fall  of  250  feet,  or  less  than  a  foot  per  mile, 
or  the  Maumee  River,  which  has  a  length  of  150  miles  and  a  fall  of  154  feet, 
or  about  a  foot  per  mile  (Clark  and  Wilson.  1912). 

The  water  in  the  normal  parts  of  the  stream  is  usually  clear  at  depths  of 
one  to  two  and  a  half  feet,  especially  on  the  riffles.  This  condition  was 
noted  in  Salt  Fork  east  of  Sidney,  and  in  the  Middle  Fork.  Above  Sidney, 
except  where  the  water  is  very  shallow,  the  stream  is  murky  and  laden  with 
fine  silt.  During  times  of  high  water  the  stream  is  in  this  condition  in  all 
parts  of  the  Big  Vermilion.  The  upper  part  of  Salt  Fork,  from  Urbana  to  aT 
point  six  or  eight  miles  down  stream  is  always  more  or  less  brownish  in 
color  from  the  large  amount  of  sewage,  equalling  as  much  as  a  third  of  the 
total  volume,  and  putrient  matter  as  well  as  an  oily  scum  is  usually  to  be 
seen  on  the  surface.  The  shore  of  the  stream  is  rendered  very  unsightly  by 
the  mass  of  filth  that  is  despoiled  above  the  usual  level  by  high  water.  At 
St.  Joseph,  ten  miles  from  Urbana,  much  the  same  condition  is  found. 

The  upper  part  of  the  Salt  Fork  has  been  greatly  modified  by  ditching 
and  dredging.  North  of  Urbana  for  the  distance  of  a  mile  and  a  quarter 
above  Crystal  Lake  Park  a  large  ditch  carries  the  surface  drainage  in  a 
straight  line  to  the  park  thus  cutting  off  the  tortuous  windings  of  the 
original  stream  bed,  which  have  been  left  as  long,  narrow,  shallow  ponds, 
reminding  one  of  the  'ox-bows'  so  common  in  the  valley  of  the  Mississippi 
River.  The  bed  of  this  ditch  is  about  six  feet  below  the  general  level  of 
the  surface.  For  several  miles  above  this  ditch  the  original  stream  has  been 
deepened  by  dredging  and  the  bed  is  now  pretty  generally  five  or  six  feet 
lower  than  that  of  the  original  stream. 

From  Crystal  Lake  Park,  Urbana,  to  a  point  near  St.  Joseph,  the  stream 
has  been  ditched  to  straighten  the  bed,  leaving  numerous  'cut-offs'  of  the 
old  stream  bed.  This  canal  permits  a  better  flow  of  water  for  the  disposal 
of  the  sewage.  Where  not  ditched  the  stream  bed  has  been  deepened. 
The  ditching  has  greatly  modified  the  original  stream  bed,  providing  a  new 
and  different  kind  of  environment  for  the  mussels  and  other  aquatic  life. 
It  is  probable  that  all  of  the  old  fauna  was  exterminated  during  the  ditching 
operations  and  the  sewage  pollution  provides  an  unfavorable  environment, 
which  the  aquatic  bottom  life  does  not  seem  able  or  inclined  to  enter.  The 
effect  of  sewage  pollution  may  be  seen  all  the  way  down  the  stream  from  the 
source  of  contamination.  At  St.  Joseph,  where  the  stream  bed  has  not  been 
modified,  conditions  are  very  bad,  the  mud  in  the  bottom  being  filled  with 
gas  forming  bacteria  which  are  constantly  causing  bubbles  of  gas  to  break 
at  the  surface  of  the  water.  Were  it  not  for  the  sewage  pollution,  the  stream 


14  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [112 

at  this  place  would  be  quite  normal  for  the  life  of  mussels  and  other  bottom 
animals.    (See  the  chapter  on  sewage  pollution.) 

Several  other  river  systems  have  their  beginning  near  Urbana  and 
Champaign,  on  the  southwest  side  of  the  Champaign  moraine.  These  are 
the  Embarras,  which  has  tributaries  rising  south  of  Urbana;  the  Kaskaskia, 
which  has  its  inception  northwest  of  Champaign  near  the  village  of  Rising; 
the  Little  Vermilion,  which  rises  in  the  southeastern  part  of  Champaign 
County;  and  the  Sangamon,  which  rises  in  the  extreme  northwestern  part 
of  Champaign  County  not  far  from  Gibson,  Only  the  last  stream  has  been 
examined  for  its  mussel  fauna  for  the  purpose  of  making  comparisons  with 
the  fauna  of  the  Big  Vermilion  River. 

The  Sangamon  River  has  a  length  of  about  180  miles  and  a  drainage 
basin  of  some  5670  square  miles.  It  rises  on  the  south  side  of  the  Blooming- 
ton  moraine  in  McLean  County,  "at  an  elevation  of  850  feet  above  sea 
level,  and  cuts  through  two  moraines  in  its  course,  the  Champaign  and  the 
Shelbyville.  The  river  channel  is  tortuous  and  meandering  and  the  flood 
plain  in  many  places  very  wide.  The  banks  of  the  stream  are  low  for  the 
most  part  and  wooded  in  spots.  The  stream  has  been  examined  carefully 
at  only  two  points,  Mahomet  and  west  of  White  Heath,  the  first  locality 
receiving  the  most  attention.  Near  Mahomet  the  river  is  notably  mean- 
dering, the  banks  are  high,  the  Champaign  moraine  rising  90  feet  above 
the  water  level  near  the  village.  The  river  bank  is  usually  five  or  six  feet 
above  the  stream,  which  has  cut  vertical  cliff-like  banks  in  many  places. 
Below  Mahomet  the  woodlands  are  abundant,  extending  well  back  from 
the  river  in  some  places.  The  river  varies  in  width  from  40  to  50  feet. 
The  bottom  alternates  between  riffles  with  sand  and  gravel  bottom  and 
deeper  back  water  stretches  with  mud  bottom.  The  former  habitats  are 
a  foot  or  so  in  depth  and  the  latter  habitats  two  to  four  feet  in  depth  in  the 
summer.  In  the  spring  the  river  is  ten  to  twelve  feet  deep  and  very  swift, 
at  times  becoming  torrential.  The  average  fall  of  the  stream  is  2.3  feet 
per  mile.  Many  logs  and  other  debris  thrown  up  on  the  flood  plains  attest 
the  power  of  the  river  during  spring  floods. 

West  of  White  Heath,  for  a  mile  above  the  I.  C.  railroad  bridge  to 
two  miles  below,  the  river  has  been  examined,  though  no  systematic 
collecting  comparable  to  that  carried  on  at  Mahomet  has  been  done.  The 
stream  in  the  portion  of  the  river  valley  examined  is  similar  to  that  near 
Mahomet  in  its  general  physiographic  features.  The  banks  of  the  stream 
are  on  the  whole  lower  than  farther  up  the  river  near  Mahomet.  Studies 
of  this  stream  similar  to  those  carried  on  in  the  Big  Vermilion  and  its 
tributaries  would  doubtless  yield  interesting  and  valuable  results.  The 
Sangamon  is  a  characteristic  mussel  stream  and  should  contain  a  much 
larger  mussel  fauna  than  at  present  known  and  listed. 


113]  FAUNA  OF  BJG  VERMIUON  RIVER— BAKER  15 


GENERAL  BIOLOGY  OF  THE  BIG  VERMILION  RIVER 

Although  the  chief  purpose  of  the  study  of  this  stream  was  to  ascertain 
the  general  conditions  and  distribution  of  the  fresh  water  MoUusca, 
especially  the  Naiades  or  river  mussels,  such  attention  was  given  to  other 
groups  as  came  easily  under  observation.  At  least  one  of  these  groups 
bears  an  intimate  relation  to  the  Naiades  in  the  matter  of  distribution 
as  restricted  by  pollution,  e.g.,  the  crayfishes,  and  another,  the  fish,  is 
closely  related  to  the  breeding  habits  of  the  mussels.  Others,  as  some  of 
the  oligochaete  worms,  are  especially  characteristic  of  polluted  waters. 
A  few  notes  are  given  under  each  group. 

The  Protozoa  and  other  microscopic  groups  are  omitted  because  given 
little  or  no  attention,  except  in  the  polluted  part  of  Salt  Fork.  These 
are  mentioned  in  the  section  on  sewage  pollution.  The  Big  Vermilion  and 
its  tributaries  present  a  wide  field  for  the  study  of  other  kinds  of  aquatic 
life  that  are  especially  characteristic  of  the  upper  reaches  of  a  river  system 

PLANTS 

The  larger  aquatic  plants  were  notably  scarce  in  most  parts  of  the 
Salt  Fork.  In  several  places  in  Salt  Fork,  especially  near  Sidney,  between 
the  cement  and  railroad  bridges,  the  shores  are  lined  with  the  spatterdock, 
Nymphaea  advena  Ait  (see  Fig.  11).  The  cat-tail,  Typha  latifolia,  Linn., 
is  common  in  various  stretches  of  the  stream,  bordering  the  shore.  The 
arrow-head,  Sagittaria  latifolia  Willd.,  and  the  larger  blue  flag.  Iris  versi- 
color, Linn.,  were  observed  along  the  shore  in  many  places.  The  water 
willow,  Dianthera  americana  Linn.,  is  abundant  in  the  shallows  in  many 
parts  of  the  Salt  Fork  below  Homer  Park.  Elodea  canadensis  Michx., 
was  abundant  at  Homer  Park. 

Filamentous  algae  occurs  in  many  places,  attached  to  submerged 
objects.  Among  these  Cladophora  and  Spirogyra  were  noted.  Septic 
algae  growing  in  the  polluted  portion  of  Salt  Fork  are  noted  under  the 
section  on  pollution  of  the  stream. 

WORMS 

Nematoda.  Gordius  robustus  Leidy,  was  collected  in  several  places  in 
Salt  Fork  between  the  first  bridge  below  St.  Joseph  and  the  bridge  above 
Sidney.  It  was  found  in  mud  bordering  the  shore,  in  shallow  water.  A 
number  of  minute  nematodes  were  observed  in  the  sludges  of  the  bottom 
in  Salt  Fork  between  Urbana  and  St.  Joseph.    These  were  not  identified. 


16  ILLINOIS  BIOLOGICAL  MONOGRAPHS  (114 

Oligochaeta.  These  aquatic  earthworms  were  abundant  in  places 
along  the  shore  of  Salt  Fork.  Sparganophilus  eiseni  Smith  occurred  in 
abundance  in  the  mud  on  the  margin  of  Salt  Fork  at  Homer  Park,  and 
immature  worm  of  this  genus,  as  well  as  cocoons,  were  collected  from  near 
the  bridge  below  St.  Joseph  to  the  bridge  above  Sidney.  A  single  specimen 
of  Helodrilus  chloroticus  (Savigny)  was  collected  in  the  Salt  Fork  near  St. 
Joseph.  This  species  has  not  heretofore  been  recorded  from  Illinois  and 
its  occurrence  at  this  locality  adds  another  species  of  earthworm  to  the 
State  list  (see  Smith,  1915:557).  Limnodrilus  was  abundant  in  bottom 
sludges  from  the  Salt  Fork,  from  Urbana  to  near  St.  Joseph.  Tubifex  was 
also  found,  but  not  as  abundantly. 

Hirudinea.  Two  species  of  leeches  occurred  in  several  places  in  Salt 
Fork,  below  St.  Joseph.  They  were  nowhere  abundant.  The  two  species 
are:  Erpohdella  punctata  (Leidy)  Moore  and  Placohdella  rugosa  (Verrill) 
Moore. 

CRUSTACEA 

Three  species  of  crayfish  (Cambarus)  were  determined  by  Professor 
Smith  from  the  material  collected  in  Salt  Fork  and  other  parts  of  the  Big 
Vermilion  River.  The  most  abundant  was  Cambarus  propinquus  Girard, 
which  was  found  commonly  from  bench  mark  655  to  the  Big  Vermilion 
River  below  Middle  Fork.  It  is  especially  abundant  in  the  latter  place 
where  an  individual  may  be  found  under  every  piece  of  stone.  The  same 
species  was  abundant  in  Stony  Creek  and  in  the  Salt  Fork  near  Muncie. 

Cambarus  blandingi  acutus  Girard,  both  young  and  adult,  occurred  in 
the  upper  parts  of  Salt  Fork,  but  preferred  a  mud  bottom  rather  than  a 
rock  bottom.  Cambarus  immunis  Hagen  was  collected  only  at  bench  mark 
655  where  it  was  rare. 

It  will  be  noted  that  Cambarus  is  first  met  with  about  two  miles  below 
St.  Joseph  and  twelve  miles  from  Urbana.  The  only  ones  seen  here  were 
dead.  Living  crayfish  begin  to  appear  in  abundance  about  six  miles  below 
St.  Joseph  or  sixteen  miles  below  Urbana.  Crayfish  and  mussels  both  be- 
come common  or  abundant  at  about  the  same  time,  viz.,  fourteen  and 
sixteen  miles  below  the  source  of  sewage  pollution  at  Urbana.  This  agree- 
ment in  distribution  indicates  the  close  relationship  between  these  other- 
wise diverse  groups  of  animals,  as  regards  resistence  to  septic  conditions, 
neither  being  able  to  thrive  under  pollutional  conditions  of  the  bottom. 

AQUATIC  INSECTS 

Aquatic  insects  are  doubtless  abundant  during  spring  and  early  summer 
in  the  lower  parts  of  Salt  Fork  and  in  the  Big  Vermilion  River.  A  few 
species  were  collected  incidentally  at  some  of  the  molluscan  stations. 
These  are  listed  in  Table  I,  in  the  order  of  their  occurrence  in  the  stream. 


115] 


FAUNA  OF  BIG  VERMILION  RIVER— BAKER 


17 


It  will  be  noted  that  the  nymph  and  larval  forms  of  most  species  appear 
coincident  with  the  degree  of  sewage  pollution.  Chironomus  and  Libellula 
are,  seemingly,  able  to  accommodate  themselves  to  the  contaminated  or 
polluted  condition  of  the  water  in  the  neighborhood  of  St.  Joseph.  The 
adult  beetles,  breathers  of  free  air,  are  not  affected  directly  by  these  un- 
favorable conditions  and  occur  in  great  abundance,  even  in  the  heavily 
polluted  parts  of  Salt  Fork  above  St.  Joseph.  The  Ephemerids  occur  for 
the  most  part  far  down  the  stream  where  the  water  is  at  most  only  con- 
taminated. The  Neuroptera  and  Plecoptera  are  clean  water  forms  and 
were  found  only  in  the  Middle  Fork  which  does  not  carry  sewage.  These 
are  also  to  be  found,  probably,  in  the  Big  Vermilion  below  Middle  Fork, 
but  no  attempt  was  made  to  discover  these  animals  when  that  part  of  the 
stream  was  examined. 

Table  I.    Distribution  of  Insects 


u 

O 

a, 

S 

1— > 

55 

■^    Si 

a 

o 

g 

01 

•c 

Xi 

a 

o  3 
1    ^ 

<u 

bo 

IH 
'C 

Xi 

i 

Diptera 
Chironomus  decorus  Joh.,  larva 

X 
X 

X 

X 

X 
X 
X 
X 
X 

X 

X 

Odonata 
Libellula  pulchella  Druiy,  nymph 

Coleoptera 

Gyrinus  analis  Say,  adult 

Dineutes  assimilis  Aube,  adult 

Cnemidolus  12-puncUitus  Say,  adult 

X 

Laccophilus  maculosus  Say,  adult 

Copelalus  glyphicus  Say  adult 

Hemiptera 

Corixa,  nymph 

X 

X 

X 

Diptera 

Cricolopus  trifascialus  F    larva  (>*) 

Ephemerida 

Hexagenia  bilineato.  Say,  nymph 

X 

Heptagenia,  nymph .    .    .  . 

X 

TricJtoptera,  larva  .... 

> 

X 

Odonata 

Ophiogomphus ,  nymph 

X 

Neuroptera 
Corydalis,  larva .... 

X 

Plecoptera 

Perla,  nymph 



X 

18  ^     ILUNOIS  BIOLOGICAL  MONOGRAPHS  [116 

HIGHER  VERTEBRATES 

Vertebrates  characteristic  of  aquatic  environments  were  fairly  common 
in  most  parts  of  the  Big  Vermilion  River  valley.  Three  species  of  turtles 
were  observed:  the  western  painted  terrapin  {Chrysemys  cinerea  Bonna- 
terre),  the  snapping  turtle  (Chelydra  serpentina  Linn.)  and  the  soft  shelled 
turtle  {Platypeltis  spinifera  LeSusur).  The  garter  snake  (Thamnophis 
sirtalis  Linn.)  was  observed  swimming  across  the  stream  in  several  places. 
The  fox  snake  (Elaphe  vulpinus  Baird  and  Girard)  was  seen  on  several 
occasions  near  the  margin  of  Salt  Fork  above  St.  Joseph.  Frogs,  among 
which  the  pickerel  frog  (Rana  palustris  LeConte)  was  noted,  were  abun- 
dant in  many  places,  and  tadpoles  of  all  ages  were  abundant  in  both  the 
Big  Vermilion  and  Sangamon  rivers. 

Aquatic  birds  were  occasionally  seen  in  both  river  valleys.  The  little 
green  heron  {Ardea  virescens  Linn.)  and  the  great  blue  heron  (Ardea  hero- 
dias  Linn.),  as  well  as  the  American  bittern  (Boiaurus  lentiginosus  Mon- 
tague) were  seen  repeatedly,  especially  in  the  old  river  cut-offs  between 
Urbana  and  St.  Joseph.  Where  high  banks  occur  the  kingfisher  {Ceryle 
alcyon  Linn.)  made  the  woods  resound  with  its  rattle-like  notes.  These 
birds  feed  largely  on  young  fish  and  in  this  way  affect  the  mussel  distribm- 
tion  by  reducing  the  number  of  fish  that  may  bear  glochidia.  Shore  birds, 
among  which  were  noted  Wilson's  snipe  {Gallinago  delicata  Ord.),  solitary 
sandpiper  {Helodromus  solitarius  Wilson),  yellowlegs  (Totanus),  sora  rail 
{Porzana  Carolina  Linn.),  and  killdeer  (Oxyechus  vociferus  Lion.).  The 
pied-billed  grebe  (Fodilymbus  podiceps  Linn.)  is  seen  frequently  during 
spring  and  autumn  on  Crystal  Lake  and  in  the  more  pond-like  reaches  of 
the  Salt  Fork.  Many  of  the  shore  birds  feed  on  moUusks  and  insects  which 
they  find  along  the  shores  of  the  Big  Vermilion  River  system.  During 
migrations,  the  river  valley  and  its  tributaries  are  fairly  alive  with  birds  of 
all  kinds,  and  at  such  times  the  region  is  well  adapted  for  bird  study. 

The  presence  of  the  muskrat  {Ondatra  zibethica  Linn.)  is  attested  by 
the  number  of  piles  of  opened  mussel  shells,  the  animals  of  which  have 
provided  this  mammal  with  many  a  meal.  In  these  muskrat  piles  have 
been  found  the  shells  of  many  species  that  are  rare  or  difficult  to  find  alive 
in  the  streams. 

The  abundance  of  all  groups  of  animal  life  in  the  Big  Vermilion  system 
indicates  that  it  is  a  favorable  environment  for  an  optimum  biota.  With 
the  exception  of  the  upper  twenty  miles  more  or  less  seriously  affected  by 
sewage  pollution,  the  stream  is  one  of  the  best  collecting  grounds  in  the 
State,  a  condition  indicated  by  the  very  large  mussel  fauna  of  thirty-eight 
species  and  races,  recorded  in  the  following  pages. 

FISH  PAUNA  OF  THE  BIG  VERMILION  RIVER 

The  close  relationship  between  the  mussel  fauna  and  the  fish  fauna, 
through  the  breeding  habits  of  the  former,  render  a  knowledge  of  the  fish 


117]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  19 

fauna  of  the  Big  Vermilion  necessary.  As  a  large  mussel  fauna  lives  in  the 
stream  it  follows  as  a  corollary  that  there  must  also  be  a  fish  fauna  of  com- 
parable size.  Fortunately,  Dr.  S.  A.  Forbes,  caused  extensive  collections 
to  be  made  in  1901,  and  these  are  listed  on  the  maps  accompanying  the 
work  on  the  Fishes  of  Illinois,  by  Forbes  and  Richardson  (1908).  Fifty 
species  are  recorded  from  the  Big  Vermilion  River  and  its  tributaries  (see 
Table  II).  It  will  be  seen  that  at  this  date  28  species  were  found  below 
Urbana,  in  that  portion  of  the  stream  now  heavily  polluted. 

Between  the  years  1908  and  1912,  the  Salt  Fork  between  Urbana  and 
St.  Joseph  was  deepened  and  straightened  and  the  bottom  fauna  was  com- 
pletely destroyed.  In  the  canal  thus  formed,  for  the  purpose  of  carrying 
ofiF  the  sewage  of  the  Twin-Cities,  no  living  clams,  crayfish,  or  other  clean 
water  animals  have  been  found,  and  but  one  school  of  young  fish  (bull- 
heads) was  observed  during  several  examinations  of  this  part  of  the  stream. 
It  is  possible  that  during  periods  of  high  water  in  the  spring,  some  hardy 
fish  may  venture  into  this  heavily  polluted  area.  Below  St.  Joseph  it  is 
quite  probable  that  some  fish  are  found  during  high  water  periods.  A 
few  minnows  were  observed  near  the  station  called  bench  mark  655,  about 
fifteen  miles  below  Urbana.  A  farm  boy  reported  that  bullheads  could  be 
caught  at  high  water  on  set  lines. 

Below  bench  mark  655,  and  for  some  distance  above  it,  fish  must  resort 
in  some  numbers  because  of  the  presence  of  a  fair  sized  mussel  fauna  (see 
Table  III).  Young  mussels,  however,  were  not  seen  in  any  number  above 
the  Homer  Park  dam,  and  it  is  possible  that  the  upper  stream  is  now  little 
visited  by  fish  suitable  for  glochidial  infection.  Below  the  dam,  young 
mussels  are  plentiful  at  all  points  examined. 

Information  concerning  the  species  of  fish  that  carry  glochidia  of  the 
river  mussels  is  still  of  a  fragmentary  character.  Suber  (1912),  Howard 
(1914),  and  other  workers  of  the  U.  S.  Bureau  of  Fisheries  haye  published 
considerable  data  on  this  subject,  but  much  more  is  needed  before  one 
can  fully  understand  the  relation  between  mussels  and  fish. 

Three  species  of  mussels  living  in  Salt  Fork  and  other  parts  of  the 
Big  Vermilion  River  are  known  to  have  glochidia  encysted  on  five  species 
of  fish,  all  of  which  have  been  reported  from  the  Big  Vermilion,  viz.: 

Mussels  Fish 

Lampsilis  anodontoides  Lepomis  humilis 

"       anodontoides  Pomoxis  spar  aides 
"      anodontoides  "      annularis 

Quadrula  metanevra  Lepomis  pallidus 

"      pustulosa  Pomoxis  annularis 

"      pustulosa  Ictalurus  punctatus 


20 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


[118 


The  abundance  of  desirable  species  of  mussels  in  the  Big  Vermilion 
indicates  that  it  may  serve  as  a  reservoir  for  button  material,  the  species 
being  easily  transported  to  laboratories  anywhere  in  the  state  for  artificial 
infection  of  fish. 

Table  II.    Distribution  of  the  Fish  Fauna  in  the  Big  Vermilion 


pq 


0^ 


f4 


Carpiodes  diffiformis  Cope.  Blunt-nosed  silver  carp 

Carpiodes  vdifer  (Raf.).  Quillback;  Silver  carp 

ErimyzoHsucettaoblongus  (Mitchill).  Chub-sucker 

Minytremamelanops  (Raf.).  Spotted  Sucker 

Catostomus  commersonii  (Lac).  Common  Sucker 

Catostomus  nigricans  (Le  Sueur).  Hog  sucker 

Moxostoma  aureolum  (LeSueur).  Common  red-horse 

Moxostoma  breviceps  (Cope).  Short-headed  red-horse 

Campostoma  anomalum  (Raf.).  Stone-roller 

Hybognathus  nucalis  Agassiz.    Silvery  minnow 

Pimephaies  notatus  (Raf.).  Blunt- nosed  minnow 

Semotilus  atromaculatus  (Mitchill).  Horned-dace 

Abramis  crysoleucas  (Mitchill).   Golden  shiner 

Cliola  vigilax  (B.  &  G.).  Bullhead  minnow 

Nolropis  cayuga  Meek.    Cayuga  minnow 

Notropis  blennius  (Girard).  Straw-colored  minnow 

Notropis  iUecebrosus  (Girard).    Minnow 

Notropis  whipplii  (Girard).  Steel-colored  minnow 

Notropis  cornutus  (Mitchill).  Common  shiner 

Nolropis  alherinoides  Raf.    Shiner 

Notropis  umbratilis  atripes  (Jordan).  Blackfin 

Ericymba  buccata  Cope.    Silver-mouthed  minnow 

Phenacobius  mirabilis  (Girard).  Sucker-mouthed  minnow 

Hybopsis  amblops  (Raf.).  Big-eyed  chub 

Hybopsis  storerianus  (Kirtland).  Storer'schub 

Hybopsis  kentuckiensis  (Raf.).  River  chub 

lotalurus  punctattis  (Raf.).  Channel-cat 

Ameiurus  natalis  (LeSueur).   Yellow  bullhead 

Atneiurus  mdas  (Raf.).  Black  bullhead 

Noturus  fiavus  Raf.  Stonecat 

Schilbeodes  gyrinus  (Mitchill).  Tadpole  cat 

Schilbeodes  mums  Qordan).  Brindled  stonecat 

Esox  vertnictdaris  Le  Sueur.   Little  pickerel 

Fundulus  notatus  (Raf.).  Top  minnow 

Labidestkes sicculus  (Cope).  Brook  silversides 


119] 


FAUNA  OF  BIG  VERMILION  RIVER— BAKER 


21 


Table  II — (continued) 


Ci 

■e 

> 
o 

< 

o 

i-i 

u 

> 

a 
o 
o 

a 

C/2 

> 

s 

a 
o 
o 

(X 
CO 

^ 

o 

-s 

pq 

ct 

3 
"do 

§ 

u 

a 

3 

"73 

CO 

-a 

1 

Q 

o 

Pomoxis  annularis  Raf .  White  crappie 

X 
X 
X 

X 

Pomoxis  sparoides  (Lacepede).  Black  crappie 

X 
X 
X 

X 
X 
X 
X 

X 

X 
X 

X 
X 

X 

X 

X 
X 

X 

Lepomis  megalotis  (Raf.).  Long-eared  sunfish 

X 

Lepomis  humilis  (Girard).  Orange-spotted  sunfish 

X 

Lepomis  paUidus  (Mitchill),   Blue  gill 

Micropterus  dolomieu  Lacepede.    Small-mouthed  black 
bass 

X 
X 

X 

Micropterus  salnwides  (Lac).  Large-mouthed  black  bass. 
Percina  caprodes  (Raf.),  Log-perch 

X 

X 
X 
X 
X 

X 

X 
X 

X 

X 
X 

X 

Hadropierus  phoxocephalus  (Nelson) 

Hadropterus  aspro  (C.  &  J.).  Black-sided  darter 

X 

X 
X 

X 

X 
X 

X 

X 

X 

X 
X 

X 
X 

X 

X 

X 

X 
X 

X 

Diplesion  hlennoides  (Raf.).  Green-sided  darter 

X 

Boleosoma  nigrum  (Raf.).  Johnny  darter 

X 

X 

Etkeostomajessiae  (Jordan  &  Bray  ton) 

X 

Etheo stoma  coeruleum  Storer.    Rainbow  darter 

X 
X 

X 
X 

X 

X 
X 

X 

X 

X 

X 

EtkeostomaflabeUare  Raf.  Fan-tailed  darter 

X 

Total  species  from  each  staticHi 

19 

34 

42 

28 

30 

27 

21 

27 

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a,  abundant 
c,  common 
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i,  gravel 
m,  mud 
(,  sand 

ij 

a^ 

a  9 

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a 

J. 

c 

I 

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Muaculium  truncatum 

Phyaa  crandaUi 

Planorbia  trivolvia 

Galba  humilia  modiceUa 

llil 

I.HI 

3  3  3.; 

iiij 

Muaculium  tranaveraum 

Ferriaaia  tardua 

Gundlachia  meekiana 

Campeloma  rufum 

Ferriaaia  rivularia 

Piaidium  compreaaum 

a    !    • 

Mi; 

lit 

Planorbia  antroaua 

Piaidium  kirklandi 

Piaidium  aplendidulum 

Sphaerium  species 

Total  species  of  mollusks 

Associated  Animals 

HelodrUua  species 

Chironomua  decoru»,  larva 

LibeUula  pukhella,  nymph 

IHneutea  aasimilia,  adult 

Cnemidotua  l2-punctatua,  adult.  . . 

Laccophilua  maculoaua.  adult 

Copelatua  glyphicua,  adult 

Cricolopus  trifaaciatua,  lar»a 

Cambarua  blandingi  acutua 

Sparganophilua  eiaeni 

Tabanua  atratua,  larva 

Erpobdella  punctata 

Placobdella  rugoaa 

Hexagenia  nymph 

Cambarua  propinguua 

Cambarua  immunii 

Corixa  nymph. 

Gordiua  robuatut 

TnchoptcTa  larva 

Ophiogomphui  nymph 

Perla  nymph 

Corydalia  larva 

Benacua  species 

24  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [122 


GENERAL  DISTRIBUTION  OF  THE  MOLLUSK  FAUNA 

It  will  be  noted  in  Table  III  that  the  mussels  were  found  in  greatest 
abundance  in  a  bottom  composed  of  sand  or  gravel,  or  both,  and  were 
fewer  in  number  of  species,  as  well  as  in  individuals,  on  a  mud  bottom. 
As  a  rule  the.  mussels  were  found  in  abundance  on  the  shallow  riflOles  and 
were  often  absent  from  the  deeper  places  in  which  the  bottom  was  composed 
of  soft  mud.  A  notable  exception  to  this  rule  occurs  at  Homer  Park  where 
the  largest  mussel  fauna  is  found  in  a  mud  bottom,  and  where  this  kind  of  a 
bottom  produced  eleven  more  species  (28)  than  did  the  sand  and  gravel 
riflBes  a  short  distance  below  (17).  This  station  has  been  used  by  Professor 
Frank  Smith  for  many  years  as  a  field  habitat  for  his  zoology  classes  and 
the  mussel  fauna  is,  therefore,  better  known  than  that  of  any  other  locality 
on  the  stream.  Although  visited  several  times  a  year  for  nearly  a  score  of 
years,  there  seems  no  diminution  of  the  fauna  in  either  species  or  individ- 
uals. A  day  spent  at  this  station,  during  which  two  collectors  examined  the 
stream,  yielded  24  of  the  28  species.  This  indicates  the  great  abundance  of 
the  fauna,  which  may  be  due  in  large  measure  to  the  aerating  influence 
of  the  dam  situated  just  above  the  collecting  grounds. 

The  stream  below  the  dam  at  Homer  Park  is  an  excellent  place  in  which 
to  study  the  ecological  conditions  governing  the  distribution  of  the  mollusk 
fauna  in  a  small  stream.  There  is  first  a  very  shallow  stream  below  the 
dam  (Fig.  14)  flowing  over  gravel  and  boulders,  in  which  a  few  gastropods 
and  small  bivalves  (Sphaerium)  live  in  considerable  abundance  (Fig.  15). 
Mussels  are  rare.  Then  follows  a  comparatively  deep  area  of  the  stream 
(2-3  feet)  flowing  over  a  bed  of  fine  sand  or  mud  in  which  mussels  are 
abundant  and  gastropods  rare  (Fig.  13).  This  is  followed  by  a  moderately 
shallow  stretch  of  the  stream  (1-2  feet)  which  flows  over  a  bottom  of  coarse 
sand  and  gravel  in  which  mussels  are  found  in  abundance,  ahhough  not  as 
numerous  in  species,  as  in  the  mud  habitat.  A  few  gastropods  live  here. 
These  conditions  are  exceptional  in  Salt  Fork  and  are  not  duplicated  in 
any  other  part  of  the  stream  above  Danville. 

Some  species  of  mussels,  as  Anodonta,  Anodontoides,  and  Uniomerus, 
prefer  a  mud  bottom  and  thrive  only  in  such  situations,  but  the  great 
majority  of  the  naiades  prefer  a  sand  or  gravel  bottom  in  water  with 
considerable  current,  and  this  is  the  reason  they  are  so  abundant  in  the 
riffles  of  all  streams.  Among  the  smaller  bivalves  (Sphaerium  and  Pisi- 
dium),  the  majority  of  species  prefer  a  mud  or  fine  sand  habitat.  Of  the 
snails  or  gastropods,  Pleurocera  and  Goniobasis  are  usually  found  in  a 


123]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  25 

rocky  (gravel)  habitat  while  Campeloma  prefers  a  mud  or  fine  sand  bot- 
tom. Physa  lives  in  both  mud  and  on  rocks  and  Ancylus  on  vegetation  or 
in  empty  shells  of  mussels.  The  ecological  preferences  of  these  species,  as 
well  as  the  associated  animals,  are  shown  in  Table  IV. 

ECOLOGICAL  VARIATION 

The  35  species  and  varieties  of  Unionidae  found  in  the  Big  Vermilion 
River  west  of  Danville  show  an  interesting  distribution.  Table  III  clearly 
indicates  that  there  is  a  more  or  less  gradual  increase  in  the  number  of 
species  as  the  stream  increases  in  size.  Taking  into  consideration  both  dead 
and  living  naiads  and  ignoring  for  the  time  the  effect  of  sewage  pollution 
on  the  distribution,  the  increase  in  species  correlated  with  the  increase  in 
distance  in  miles  from  Urbana  may  be  expressed  in  the  following  table: 

Table  Number  V.  Inckease  in  Species  with  Distance 

Station  No.  of  Species        Distance  from  Urbana 

Big  bend 6  14 .  25  m'les 

One  mile  north  iron  bridge 12  16 .  50  " 

Railroad  bridge 15  20.00  " 

Two  miles  above  Homer  dam 14  24 .  75  " 

Homer  Park 28  27.00  " 

South  of  Muncie 23  36.00  " 

Salt  Fork  junction 15  44.00  " 

Middle  Fork 22  45.00  " 

BigVermUion , . ..  21  46.00  " 

The  sudden  rise  in  number  of  species  at  Homer  Park  is  noteworthy  and 
is  due  to  the  exceptionally  favorable  environment,  good  depth  of  water, 
favorable  bottom,  plenty  of  food,  and  a  fully  normal  supply  of  dissolved 
oxygen  provided  by  the  dam  just  above  the  Park.  The  dam  appears  to  be 
an  effective  barrier  to  the  migration  of  mussels,  and  it  would  also  seem 
difficult  for  fish  to  pass  the  dam,  except  at  very  high  water,  and  thus 
migration  in  the  glochidial  stage  is  rendered  difl&cult  or  impossible.  In 
the  table  it  may  be  noted  that  17  species  occur  at  five  stations,  two  to 
eight  miles  above  the  dam  and  28  species  occur  below  the  dam.  Seventeen 
species  are  common  to  both  areas  and  12  species  are  found  below  but  not 
above  the  dam.    This  distribution  is  shown  in  Table  VI. 

A  striking  feature  of  naiad  distribution,  noted  repeatedly  in  several 
species,  is  the  conspicuous  change  in  the  shape  of  the  shell  as  the  distance 
from  the  headwaters  of  the  stream  increases.  Species  that  normally  have 
swollen  or  globose  shells  in  the  larger  rivers,  occur  as  flat  or  compressed 
forms-in  the  headwaters  of  these  streams.  An  increase  in  length  of  shell 
as  correlated  with  decreased  obesity  is  also  noted,  and  also,  a  decrease  in 
tuberosity.  Ortmann  (1920)  has  recently  ably  discussed  this  matter  and 
shows  that  the  rule  holds  good  for  many  species  in  widely  separated  areas; 
the  writer  cannot  fully  agree  with  Ortmann  in  reducing  so  many  species 


26  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [124 

of  Naiades  to  varieties  on  the  basis  of  compression  in  the  headwaters  of 
streams.  The  same  species  varies  in  obesity,  but  it  is  the  same  species, 
whether  thin  or  fat.  Other  characters  are  usually  present  which  separate 
the  allied  species. 

Table  VI.    Species  or  Uniontdae  Found  Above  and  Below  Hoicsr  Park  Dam 

Both  Above  and  Below  Dam  Below  Dam  Only 

paroa  anodontoides 

ferussacianus  dlipsiformis 

grandis  ligamentina 

imbecillis  mtdtiradiata 

edentulus  lackrymosa 

pavonius  melanevra 

luteola  xvardii 

lienosa  R.  tuberculata 

complanata  T.  tuberculata 

rubiginosa  circulus 

undulata  clava 

pustulosa  glans 
costata 
marginala 
cocfineum 
ventricosa 
compressa 

In  the  Big  Vermilicwi  this  variation  in  compression  is  marked  in  several 
species.  Thus  Rotundaria  tuberculata,  Pleurobema  coccineum,  and  Amblema 
are  more  compressed  than  are  individuals  from  the  Wabash  River  below 
the  junction  of  the  Big  Vermilion  with  that  river.  Quadrula  pustulosa  is 
smaller  than  the  same  species  lower  down  in  the  Salt  Fork,  and  the  same 
may  be  said  of  Alasmidonta  marginata  and  Strophitus  edentulus.  That  the 
rule  does  not  always  hold  good  is  shown  by  the  variation  of  Fusconia  rubi- 
ginosa  which  is  abundant  in  most  parts  of  the  Big  Vermilion  and  its  tribu- 
taries. Measurements  are  given  in  Table  VII,  showing  the  length  and 
breadth  of  several  species  in  different  parts  of  the  Salt  Fork  from  below 
Urbana  to  the  Big  Vermilion.  The  percentage  of  width  to  length  is  also 
shown. 

It  will  be  seen  that  the  average  index  for  the  first  lot  is  42  per  cent  and 
for  the  last  lot,  46  miles  down  stream,  is  almost  the  same,  45  per  cent. 
These  averages  compare  well  with  some  of  those  given  by  Ortmann  (1920: 
283).  It  was  observed,  however,  that  in  the  Salt  Fork  and  Big  Vermilion 
the  obese  individuals  occurred  with  the  compressed  specimens  the  former 
increasing  in  ratios  as  the  distance  down  stream  increased.  The  variety 
wardii  of  Quadrula  metanevra  occurred  in  two  places  in  Salt  Fork  but  always 
in  company  with  the  typical  form.  In  the  cases  cited  above  ecological 
features  cannot  be  called  into  account  in  locating  the  cause  of  the  com- 


1251  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  27 

pression  of  the  shell,  for  all  live  in  the  same  section  of  the  stream  under 
identical  conditions.  The  rule  cited  by  Ortmann,  however,  seems  to  be 
applicable  in  most  cases. 

Several  species  increase  in  size  toward  the  lower  part  of  the  river.  This 
is  especially  true  of  Anodonta  grandis,  Strophitus  edentulus,  Alasmidonta 
marginata,  Eurynia  lienosa,  LampsUis  luteola,  Amblema  undulata,  and 
Lampsilis  ventricosa.  A  few  others  show  some  increase  at  different  stations. 
One  species,  Uniomerus  tetralasmus,  is  apparently  confined  to  the  upper, 
smaller  tributary  streams  of  Salt  Fork.  It  was  common  in  the  ditch  north 
of  Urbana;  in  Crystal  Lake,  Urbana,  in  Spoon  River;  and  at  Muncie  in  a 
small  tributary.  Two  broken  valves  were  found  at  the  station  called  the 
natural  dam,  but  these  are  believed  to  have  been  washed  into  this  stream 
from  a  nearby  tributary  which  was  dry  when  this  part  of  the  Salt  Fork 
was  examined  (September  25).     Tetralasmus  probably  also  occurs  in  the 

Table  VII.    Variation  of  Fusconaia  Rubiginosa 

Length  Width  Per  cent  Station  No.  Distance  from 

Urbana 

58  23  39  17  15M  miles 

62  26  42  ..                   

61  31  50  ..                   

68  27  39                                             

79  33  42                                             

86  33  38  24  24^  miles 

89  41  46                                             

90  31  34  25  27     miles 

82  35  42  ..                   

89  47  52                                             

71  30  42  26  36  miles 

67  30  44                  

102  41  40  30       46  mUes 

65  30         46  ..        

86  43  SO  ..        

upper  part  of  Middle  Fork  and  in  North  Fork,  but  the  upper  parts  of  these 
streams  have  not  been  examined.  The  majority  of  the  other  species  occur 
at  several  stations  along  the  Salt  Fork  and  its  tributaries  and  no  particular 
variation  in  distribution  was  observed  except  as  already  noted. 

Three  mussel  species  and  varieties  were  found  in  Crystal  Lake  that 
are  exotic  as  far  as  the  Big  Vermilion  River  is  concerned.  These  are  Ano- 
danta  grandis  gigantea,  Anodonta  corpulenta,  and  Uniomerus  tetralasmus 
sayii.  These  species  were  artificially  introduced  into  this  body  of  water 
about  1908  by  a  member  of  the  zoological  department  of  the  University  of 
Illinois.  They  originally  came  from  a  stream  in  western  Indiana.  That 
these  mussels  found  a  favorable  environment  and  have  thrived  during  these 
years  is  evidenced  by  the  number  of  fine  specimens  recently  collected  when 
the  lake  was  partly  drained.  Only  the  Uniomerus  was  rare,  but  one  speci- 
men being  found.    As  Crystal  Lake  is  not  connected  with  the  Salt  Fork 


28 


ILUNOIS  BIOLOGICAL  MONOGRAPHS 


(126 


stream,  these  species  have  not  been  able  to  enter  the  Big  Vermilion  drain- 
age. 

As  has  been  noted  in  the  Illinois  River  (Forbes  and  Richardson,  1919), 
the  mussel  fauna  gradually  increases  as  the  distance  from  the  source  of 
sewage  pollution  becomes  greater.  In  the  Salt  Fork  the  fauna  becomes 
normal  at  about  20  miles  from  the  source  of  pollution  at  Urbana.  In  the 
Illinois  River  a  normal  fauna  is  not  found  within  80  miles  (Hennepin)  of 
the  source  of  pollution  indicating  that  the  quantity  of  sewage  is  so  great 
that  the  river  must  flow  this  distance  before  purifying  itself  sufficiently  for 
the  residence  of  normal  aquatic  life.  That  a  normal  fauna  should  be 
found  within  20  miles  of  the  source  of  pollution  in  the  Salt  Fork,  though  a 
much  smaller  stream  carrying  a  smaller  amount  of  sewage,  is  quite  sur- 
prising when  it  is  remembered  that  no  large  tributaries  enter  the  stream 
above  Spoon  River,  and  indicates  that  self  purification  is  active.  The 
shallowness  of  the  water  (less  than  a  foot  on  the  average  in  fall  and  winter) 
probably  provides  a  larger  quantity  of  dissolved  oxygen  than  wou'ld  be 
possible  in  waters  of  a  deeper  stream.  It  was  especially  noted  that  Am- 
blema  undulata  and  Lasmigona  complanata,  of  the  larger  species,  withstood 
the  absence  of  water  better  than  any  of  the  other  comparable  species. 
These  mussels  also  resisted  polluted  conditions  better  than  others  and  this 
fact  is  important  in  connection  with  mussel  propagation  for  button  shells. 

COMPARISONS  WITH  OTHER  RIVER  SYSTEMS 

It  is  of  interest  and  value  to  compare  the  mussel  fauna  of  the  Big 
Vermilion  River  with  that  of  some  other  rivers  of  comparable  size  and 
development.  The  United  States  Bureau  of  Fisheries  has  conducted 
mussel  investigations  of  several  of  the  rivers  of  Illinois  and  adjacent  states 
and  one  of  these,  the  Kankakee  (Wilson  and  Clark,  1912),  may  weU  be 
compared  with  the  Big  Vermilion.  The  mussel  fauna  of  the  Sangamon 
River  is  also  included,  the  data  given  being  gathered  from  several  sources, 
but  principally  from  personal  collections  and  from  collections  in  the 
Museum  of  Natural  History  of  the  University  of  Illinois.  Some  species 
not  listed  by  Wilson  and  Clark  are  included  from  Baker's  Catalog  of 
Illinois  Mollusca  (1906).    These  are  indicated  by  an  asterisk. 

Table  VIII.    Distkibution  of  Unionidae  in  Three  River  Systems 


Length  of  river  in  miles 

Quadrula  cylindrica 

"       metanevra 

"       metanevra  wardii. . . 

"      pustulosa 

"       lackrymosa 

"       ebena 

Trilogonia  tuber culala 

Amblema  undttUta 

"       peruviana  (plicata). 


Vermilion 
90 

z 
z 
z 
z 
z 


Kankakee 
300 


Sangamon 
150 


127] 


FAUNA  OF  BIG  VERMIUON  RIVER— BAKER 


29 


Table  VTII — (continued) 


Fusconaia  rubiginosa 

"  trigona 

"  solida 

Rotundaria  tuberculata 

Pleurobema  clava 

"  coccineum 

Plelhobasus  aesopus 

EUiplio  gibbosus 

Uniomerus  tetralasmus 

"         tetralasmus  sayii 

Strophitus  edenttdus 

"         edentulus  pavonitts 

Anodonla  grandis 

"       grandis  gigantea 

"       corpulenta 

"       imbeciUis 

Anodontoides  ferussacianus 

"       /.  buchanensis 

Arcidens  confragosus 

Lasmigona  compressa 

"        costata 

"        complanata 

Alasmidonta  marginata 

"         calceola 

Ptychobranchus  phaseolus 

Obliquaria  reflexa 

Plagiola  securis 

Amygdalonaias  elegans 

"         donacifortnis 

Propter  a  alata 

Paraptera  gracilis 

Obovaria  circulus 

"      ellipsis 

Actinonaias  ligamenlina 

"       ligamentina  nigrescens. 

"        dlipsiformis 

Carunculina  parva 

"         glans 

Eurynia  recta 

"      subrostrata 

"      iris 


"     fabalis 

"     lienosa 

Latnpsilis  fallaciosa 

"      anodontoides 

"      ventricosa 

"      multiradiats 

"      capax 

"      luteola 

"      higginsi 

Truncilla  sulcata 

"      perplexa  rangiana . 


Total  species  in  each  river. 


Vermilion 

X 


38 


Kankakee 


Sangamon 

X 


48 


25 


30  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [128 

It  is  noteworthy  that  with  a  length  of  300  miles  and  with  two  tributa- 
ries of  large  size  (Iroquois  River,  100  miles  in  length,  Yellow  River,  65  miles 
long)  the  Kankakee  River  has  a  mussel  fauna  only  21  per  cent  greater  than 
the  Big  Vermilion  River  with  a  length  of  90  miles  and  no  very  long  tribu- 
taries. Other  species  will  proably  be  found  in  the  Big  Vermilion  below 
Danville,  which  was  not  examined  during  this  survey,  and  these  may 
bring  the  total  nearer  to  that  of  the  Kankakee  River.  The  Sangamon 
River  undoubtedly  contains  many  more  species  than  listed  in  the  table, 
and  these  will  be  found  when  additional  collecting  is  carried  on.  The  table 
shows  that  the  mussel  fauna  of  the  Big  Vermilion  River  is  of  large  size  as 
compared  with  other  streams  of  similar  character. 


129]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  31 


SYSTEMATIC  DISCUSSION  OF  THE  MOLLUSCA 

In  this  chapter  the  species  of  mollusks,  both  Pelecypoda  (mussels, 
clams)  and  Gastropoda  (snails),  are  discussed  in  relation  to  their  distribu- 
tion in  the  Big  Vermilion  River,  special  emphasis  being  given  the  Unionidae 
or  river  mussels  on  account  of  their  economic  importance.  The  influence  of 
sewage  pollution  of  the  stream  on  the  molli^sk  fauna  is  also  referred  to. 
The  species  collected  in  the  Sangamon  River  at  Mahomet  and  elsewhere  are 
included  for  purposes  of  comparison. 

The  classification  followed  for  the  Unionidae  is  that  proposed  by  Simp- 
son (1900,  1914)  and  extended  by  Ortmann  (1912,  1918).  The  sequence  of 
groups  is  that  set  forth  in  Walker's  Synopsis  recently  published  (1918). 
It  will  be  noted  that  the  newer  classification  necessitates  the  adoption  of 
several  new  names,  both  generic  and  specific,  but  these  seem,  on  the 
whole,  justified  by  the  rules  of  nomenclature  and  are  a  natural  result  of 
the  advancement  of  knowledge  on  the  subject. 

For  the  purpose  of  providing  reliable  data  on  the  particular  character- 
istics of  the  mussels  and  other  mollusks  in  this  stream  for  comparison  with 
similar  features  of  this  group  of  animals  in  other  streams,  a  feature  almost 
totally  lacking  in  the  literature,  considerable  space  is  devoted  to  descrip- 
tions of  the  minor  variations  and  pathological  conditions  of  each  species 
in  different  environments.  This  has  been  done,  more  or  less  extensively, 
in  several  reports  on  the  mussel  faunas  of  three  or  four  of  our  Illinois, 
Indiana,  and  other  streams  (Wilson  and  Clark,  Danglade).  It  will  be 
noted  that  there  are  certain  features  characteristic  of  the  species  in  one 
stream  not  shared  by  the  same  species  in  other  streams,  as,  for  example, 
Lampsilis  ventricosa  which  differs  markedly  in  coloration  and  even  in 
shape  in  the  two  river  systems  herein  considered.  Similar  data  on  our  other 
rivers  would  provide  a  body  of  facts  of  considerable  importance, 

FAMILY  UNIONIDAE 

1.  Quadrula  (Quadrula)  cylindrica  (Say).    Rabbits-Foot. 

This  species  was  not  found  in  the  Salt  Fork  above  a  point  about  a  mile 
west  of  its  junction  with  the  Middle  Fork,  44  miles  from  Urbana.  As  it  is 
not  listed  from  the  neighborhood  of  Muncie  its  westward  extension  in 
the  stream  lies  somewhere  between  Muncie  and  Middle  Fork.  Even  in 
this  part  of  the  river  it  is  rare  and  the  specimens  obtained  are  small,  of 
dark  color  and  resemble  the  form  called  strigillatus  by  Wright.  Cylindrica 
is  not  a  widely  distributed  species  in  Illinois,  if  one  may  judge  by  the 
records  at  hand.     Danglade  (1914)  did  not  find  it  in  the  Illinois  River 


32  ILLINOIS  BIOLOGICAL  MONOGRAPHS  (130 

"nor  is  it  listed  by  other  students.  It  has  been  reported  by  several  concholo- 
gists  from  the  Wabash  River  (Baker,  1906:79)  and  the  Ohio  River,  in  which 
streams  it  is  common  and  of  large  size  and  fine  color.  The  species  probably 
would  not  thrive  in  polluted  water.  It  was  not  found  in  the  Sangamon 
River  at  the  places  visited.  Owing  to  its  peculiar  shape  it  is  not  adapted 
for  the  cutting  of  button  blanks  and  is  considered  worthless  by  the  mussel 
fishermen. 

2.  Quadrula  (Quadrala)  metanevra  Rafinesque.    Monkey-Face. 

This  naiad  is  apparently  a  rare  species  in  Salt  Fork  occurring  sparingly 
from  Homer  Park  to  Middle  Fork.  It  begins  to  increase  in  number  of 
individuals  near  the  Middle  Fork,  where  the  specimens  are  also  larger 
and  more  brilliantly  colored.  All  but  one  of  the  specimens  collected  are 
typical  in  form  and  coloring.  Individuals  from  the  Big  Vermilion  below 
Middle  Fork  are  larger  than  those  collected  above  this  point.  The  species 
is  also  more  abundant.  It  is  found  on  both  a  mud  and  a  gravel-sand  bot- 
tom. Specimens  from  Homer  Park  are  darker  and  less  conspicuously  rayed 
than  those  from  Middle  Fork,  and  are  also  less  pustulose.  Metanevra  is 
rare  in  the  Sangamon  River,  living  on  both  a  sand  and  gravel  bottom. 

2a.  Quadrula  (Quadrula)  metanevra  wardii  (Lea). 

Two  specimens  referable  to  this  variety  have  been  collected  from  the 
Big  Vermilion;  one  near  Muncie,  in  the  Salt  Fork,  and  one  in  the  Middle 
Fork,  above  its  entrance  into  the  Vermilion  River.  These  individuak 
are  more  elongated  and  compressed  than  the  typical  form  and  the  tubercles 
are  not  as  heavy,  in  fact  are  reduced  to  large  pustules.  Professor  Smith 
has  found  the  variety  more  common  in  the  Sangamon  River  than  tlie 
typical  form,  and  until  these  two  specimens  were  found  in  the  Big  Vermilion 
drainage,  wardii  was  supposed  to  be  the  predominant  form  in  the  Sanga- 
mon while  the  typical  form  was  believed  to  be  the  only  form  of  this  species 
found  in  the  Big  Vermilion,  at  least  above  Danville.  Wardii  i^,  as  far  as 
present  material  indicates,  very  rare  in  the  Salt  Fork  and  other  tributaries 
of  the  Big  Vermilion. 

3.  Quadrula  (Theliderma)  pustulosa  (Lea).  Warty-Back;  Pimple-Back. 
This  is  the  most  abundant  Quadrula  in  both  the  Salt  Fork  and  the  San- 
gamon River,  rivalling  in  number  any  other  mussel  species  in  the  lower 
part  of  the  Salt  Fork.  It  does  not  occur  in  any  abundance  above  the 
Homer  Park  dam,  but  below  this  point  it  is  common,  of  large  size,  fine 
color,  and  good  nacre.  The  sewage  pollution  has  evidently  afiFected  this 
species  as  others  and,  with  rare  exceptions,  only  dead  shells  could  be  found 
above  the  Homer  Park  dam.  Below  the  dam  it  occurs  commonly  and  the 
increase  in  number  of  individuals  is  largely  due  to  the  aerating  effect  of 
the  flow  of  water  over  the  dam  which  provides  the  dissolved  oxygen  so 


131]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  33 

necessary  to  these  animals.  The  young  shells  (20mm.  in  length)  are  almost 
smooth  with  a  broad  dark  green  ray  or  stripe  extending  from  the  umbones 
to  the  ventral  margin  of  the  valve.  No  young  shells  were  found  in  the 
stream  above  Homer  Park  dam  and  the  species  may  not  be  breeding  in 
this  part  of  the  stream  at  the  present  time. 

The  pustulosa  from  Salt  Fork  exhibit  some  variation  in  the  pustulosity 
of  the  surface,  but  all  are  referable  to  typical  pustulosa.  A  few  specimens 
from  Homer  Park  are  more  quadrate  than  the  average  but  are  otherwise 
typical.  The  individuals  from  the  Sangamon  River,  however,  show  con- 
siderable variation  in  both  form  and  pustulosity,  ranging  from  nearly 
circular  to  quadrate  and  from  almost  smooth  to  quite  pusttflose.  On  an 
average,  however,  they  are  less  pustulose  than  the  species  occurs  in  Salt 
Fork.  Individuals  might  be  picked  out  that  could  be  referred  to  both 
dorfeuillianus  Lea  and  schooler aftensis  Lea,  but  the  range  of  variation  is  so 
great  that  they  seem  better  referred  to  pustulosa.  In  the  Sangamon  River 
pustulosa  occurs  on  a  sand  and  gravel  bottom  but  in  the  Big  Vermilion 
River  it  is  found  most  abundantly  on  a  mud  bottom.  The  individuals 
from  Homer  Park  and  the  Sangamon  River,  especially  the  later,  are  of 
good  size,  70  to  80mm.  in  length,  and  the  thickness  of  the  shell  combined 
with  the  clear  pearly  luster  would  seem  to  make  them  good  shells  for  the 
button  trade.  No  evidences  of  parasitism  were  observed  in  the  shells 
examined. 

4.  Quadrula  (Theliderma)  lachrymosa  (Lea).    Maple-Leaf. 

This  handsome  shell  is  very  rare  in  the  Salt  Fork  and  was  not  found 
at  any  of  the  localities  in  the  Sangamon  River.  In  the  Salt  Fork  it  has 
been  found  only  at  Homer  Park  below  the  dam,  and  only  occasional  speci- 
mens have  been  collected  here.    These  are  quite  typical  of  the  species. 

5.  Tritogonia  tuberculata  (Barnes).    Buck-Horn;  Pistol-Grip. 

The  buck-horn  first  makes  its  appearance  in  Salt  Fork  at  Homer  Park 
below  the  dam  where  it  is  of  large  size  (female  145,  male  115  mm.)  and  fine 
quality.  The  shells  are  densely  covered  with  tear-like  pustules  which  in  a 
few  individuals  cover  the  entire  surface,  though  usually  confined  to  the 
middle  and  anterior  end  behind  the  posterior  elevated  ridge.  Of  the  speci- 
mens collected  40  percent  are  males.  Young  specimens  46  mm.  in  length 
were  found  at  Homer  Park.  Individuals  from  Homer  Park  are  larger  than 
those  collected  in  the  Sangamon  River,  the  largest  specimens  being  found 
on  a  mud  bottom,  although  it  also  lives  on  a  sand  and  gravel  bottom.  Both 
the  Salt  Fork  and  Sangamon  specimens  are  of  good  quality  from  the  button 
makers  standpoint. 

Abnormalities  and  pearly  growths  due  to  injuries  or  parasitism  are 
rare  in  the  specimens  of  this  species  examined.  A  few  individuals  from 
Homer  Park  had  scattered  pin-head  pearls  and  a  small  patch  of  discolored 


34  JLUNOJS  BIOLOGICAL  MONOGRAPHS  (132 

blister  formation  near  the  anterior  and  posterior  end,  one  in  each  end  of 
two  specimens. 

6.  Amblema  nndulata  (Barnes).    Blue-Point;  Three-Ridge. 

This  characteristic  mussel  is  the  most  abimdant  species  in  the  Vermilion 
River,  greatly  exceeding  (with  the  possible  exception  of  Lasmigona  com- 
planata)  in  number  of  indi\aduals  all  other  species.  It  is  also  able  to  resist 
much  of  the  ill  effects  of  sewage  pollution  and  is  the  first  shell  met  with  in 
the  polluted  waters  of  the  Salt  Fork.  Living  specimens,  however,  were 
not  seen  above  the  starion  called  bench  mark  655,  a  distance  of  over  15 
miles  from  the  source  of  pollution.  Empty  shells  and  odd  valves  occur 
more  or  less  abundantly  from  St.  Joseph,  10  miles  below  Urbana,  to  the 
station  mentioned.  As  the  species  lives  in  fair  abimdance  in  the  tributary 
known  as  Spoon  River,  for  a  distance  of  over  two  miles  up  stream  from  near 
the  mouth  of  the  stream,  it  is  evident  that  at  one  time  its  distribution  was 
equally  continuous  in  the  Salt  Fork  below  the  jimction  of  Spoon  River 
with  Salt  Fork,  where  now  there  is  a  break  of  nearly  six  miles.  This  break 
in  the  distribution  is  in  all  probability  due  to  the  sewage  pollution,  for  the 
stream  is  admirably  adapted  by  nature  as  a  habitat  for  this  species  and 
has  not  been  disturbed  by  dredging. 

There  is  great  variation  in  the  form  of  the  shell.  Many  specimens  from 
the  upper  part  of  the  stream,  both  Spoon  River  and  Salt  Fork  as  far  down 
as  the  natural  dam,  are  almost  roimd  with  a  broad  'wing'  above  the  undula- 
tions, which  may  be  reduced  in  number  and  form  (Fig.  34).  These 
shells  may  be  inflated  or  rather  compressed.  Other  shells  are  more  quad- 
rate and  in  occasional  individuals  the  umbones  are  elevated  simulating 
Amblema  peruvumc  {plicata  of  authors).  These  shells  have  a  black  or 
dark  brown  epidermis  in  the  adult  condition.  In  Spoon  River  young 
sheUs  25  mm.  long  were  common,  but  few  yoimg  specimens  were  foxmd  in 
the  Salt  Fork  above  the  Homer  Park  dam.  Shells  from  the  lower  part  of 
Salt  Fork,  below  Sidney,  are  as  a  rule  cleaner,  the  epidermis  is  of  a  brighter, 
lighter  brown  and  are  more  uniformly  quadrate  than  those  from  above 
Sidney.  The  largest  specimen  collected  measured  140  mm.  in  length  and 
this  seems  to  be  the  maximum  size  for  the  undulaia  in  this  stream.  Many 
of  this  size  were  seen. 

In  the  Spoon  River,  and  in  the  upper  part  of  Salt  Fork,  injured  shells 
are  common.  The  injuries  consist  of  breaks  in  the  shells  and  subsequent 
repairs.  In  one  specimen  from  the  upper  part  of  Spoon  River,  an  injury 
had  been  received  when  the  mussel  was  small  which  resulted  in  a  deep 
channel  across  the  right  valve  (Fig.  29)  and  a  ridge,  also  slightly  chan- 
neUed,  on  the  left  valve  (Fig.  30).  Another  sheU  had  nearly  a  hundred 
blister  pearls  on  the  edge  of  the  posterior  margin  of  the  left  valve  (Fig.  28) 
and  a  large  blister  pearl  about  midway  of  the  paUial  line  in  the  right  valve 


133]  FA  UNA  OF  BIG  VERMILION  RIVER— BAKER  35 

(Fig.  27).  Still  another  shell  had  covered  a  quantity  of  mud,  which  had 
gotten  in  between  the  mantel  of  the  animal  and  the  shell,  with  a  thin  layer 
of  pearl,  forming  a  large  pad-like  blister  covering  the  greater  part  of  the 
interior  of  the  left  valve  (Fig,  26).  The  right  valve  was  normal  (Fig.  25). 
These  blister  pearls,  as  well  as  the  more  valuable  free  pearls,  are  believed 
to  be  caused  by  parasites,  perhaps  distomids.  These  injured  shells  are 
eagerly  sought  by  the  pearl  hunters  and  mussel  fishermen  in  the  belief 
that  they  may  contain  pearls  of  value. 

The  undulata  from  the  Sangamon  River  also  exhibit  a  wide  range  of 
variation  in  the  shape  of  the  shell,  but  not  to  the  degree  seen  in  the  material 
from  the  Spoon  River  and  Salt  Fork  of  the  Big  Vermilion  River.  In  the 
Sangamon,  undulata  is  very  abundant  on  a  gravel  and  sand  bottom. 
In  the  branches  of  the  Big  Vermilion  it  occurs  on  both  a  mud  and  a  sand- 
gravel  bottom.  As  this  species  is  very  successful  in  resisting  adverse 
conditions  it  is  a  valuable  mussel  for  propagation  in  the  streams  subject 
to  pollution.  It  is  probably  not  much  afifected  by  a  moderate  amount  of 
sewage  in  its  environment.  The  button  manufacturers  consider  it  a  good 
shell  when  the  undulations  are  not  too  heavy  to  render  the  cutting  of 
blanks  difficult. 

7.  Fuscunaia  rubiglnosa  (Lea).    Wabash  Pig-Toe. 

This  mussel  is  abundant  in  the  lower  part  of  the  Salt  Fork.  It  was  not 
found  in  any  abundance  above  the  dam  at  Homer  Park,  where  it  is  abun- 
dant, and  the  large  number  of  dead,  empty  shells  observed  attest  the 
presence  of  an  unfavorable  environment.  As  it  is  rare  in  Spoon  River, 
where  some  other  species  are  abundant,  it  is  probable  that  this  species 
requires  fairly  deep  water  and  a  large  stream  bed  to  attain  good  size  and 
abundance  in  individuals.  This  characteristic  of  distribution  was  also 
noted  by  Wilson  and  Clark  (1912:43)  in  the  Kankakee  River  where  rubigi- 
nosa  was  found  to  be  more  common  in  the  lower  part  of  the  river. 

There  is  considerable  variation  in  the  form  of  the  shell;  some  examples 
are  compressed,  others  quite  inflated.  Nearly  all  are  distinctly  quadrate, 
but  in  some  examples  the  ventral  margin  is  convex;  in  others  it  is  some- 
what concave;  while  in  a  few  it  is  straight.  The  individuals  from  the 
upper  part  of  the  stream,  above  Homer  Park  dam,  are  usually  dark  brown 
with  a  satiny  sheen  to  the  epidermis  and  are  almost  rayless.  Those  from 
the  lower  part  of  the  river,  especially  from  Middle  Fork,  are  light  yellowish 
brown,  quite  distinctly  rayed.  The  nacre  varies  from  white  to  pink  or 
salmon,  but  is  white  in  the  great  majority  of  specimens  collected.  Young 
shells  28  mm.  in  length  were  common  below  the  Homer  Park  dam,  but  were 
apparently  rare  above  the  dam.  This  may  indicate  adverse  conditions 
due  to  sewage  pollution  and  the  species  may  not  now  be  breeding  freely, 
possibly  for  lack  of  suitable  fish  for  the  glochidia.     Young  specimens  were 


36  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [134 

also  collected  in  the  Big  Vermilion  River.  One  of  the  largest  adult  individ- 
uals found,  below  Homer  Park  dam,  measured  95  mm.  in  length;  another 
from  the  Big  Vermilion  River  measured  103  mm.  in  length.  The  species 
occurs  about  equally  on  a  mud  or  sand-gravel  bottom. 

A  single  example  from  Homer  Park  is  worthy  of  special  note.  It  is 
large,  inflated,  almost  twice  as  wide  as  the  average  shell  of  the  same  size, 
and  is  elongate-quadrate  in  outline.  When  viewed  from  within,  the 
valves  are  basin-shaped.  All  of  the  muscle  scars  are  very  heavily  impressed 
and  the  pseudocardinal  teeth  are  much  modified  and  heavier  than  in  normal 
rubiginosa.  The  lateral  teeth  are  very  high,  wide  and  massive.  The 
shell  was  dead  when  picked  up  and  badly  discolored  and  notes  on  the  ani- 
mal, which  would  have  been  very  desirable,  could  not  be  made.  The 
measurements  of  this  shell,  together  with  that  of  a  normal  shell  of  the 
species,  from  the  same  habitat,  are  given  below: 

Length,  90;  height,  59;  width,  50  mm.    Z11163  A,  Variety. 
"      82        "      58         "    36  mm.    Zl  1163  B,  Normal. 

This  species  also  occurs  in  the  Sangamon  River,  but  does  not,  appar- 
ently, attain  the  dimensions  of  the  Salt  Fork  specimens,  nor  does  it  occur 
as  abunantly.  There  is  but  slight  variation  in  form  in  the  Sangamon 
shells.  No  pathological  specimens  were  observed  in  individuals  from  either 
river.  Rubiginosa  is  not  much  esteemed  by  either  pearlers  or  mussel  fisher- 
men. 

Rubiginosa  frequently  closely  resembles  Pleurobema  coccineum  in  the 
form  of  the  shell  and  specimens  occur  which  seem  difficult  to  place  satisfac- 
torily. The  animals  differ  in  that  in  rubiginosa  all  four  of  the  gills  are  used 
as  marsupia  while  in  coccineum  only  the  outer  gills  are  so  used.  As  far  as 
the  Salt  Fork  and  Sangamon  River  shells  are  concerned  there  has  been  no 
difficulty  in  placing  any  individual.  In  this  material  rubiginosa  is  always 
quadrate  with  the  umbones  large  and  full,  the  posterior  end  of  shell  is 
almost  sharply  truncated  and  there  is  a  more  or  less  distinct  ridge  extend- 
ing from  the  umbones  to  the  posterior  angle  of  the  shell.  In  coccineum 
the  outline  is  rather  ovate,  or  rounded,  there  is  no  posterior  ridge  and  the 
position  of  the  umbones  gives  to  the  shell  an  oblique  appearance  which  is 
very  characteristic  and  is  absent  in  rubiginosa.  The  ventral  margin  in 
coccineum  is  almost  always  convex  and  seldom  straight  or  concave  as  in 
rubiginosa.  The  young  shell  in  coccineum  is  also  usually  more  distinctly 
rayed.  The  surface  of  the  two  species  is  also  different,  that  of  coccineum 
not  being  'satiny'  as  is  that  of  rubiginosa.  The  interior,  and  even  the 
exterior,  of  coccineum  is  usually  pinkish  or  salmon  colored,  although 
individuals  occur  with  white  nacre. 


135]  FA  UNA  OF  BIG  VERMILION  RIVER— BAKER  37 

8.  Pleurobema  clava  (Lamarck).    Club-Shell. 

This  species  is  rare  in  most  parts  of  the  Big  Vermilion  examined,  and 
was  not  found  in  the  Sangamon.  It  occurs  sparingly  at  Homer  Park, 
abundantly  in  the  Salt  Fork  near  Muncie,  and  sparingly  in  the  Middle 
Fork,  At  Muncie  the  largest  specimen  measured  90  mm.  in  length.  The 
specimens  from  the  Big  Vermilion  are  beautifully  marked  with  broad  green 
rays  on  young  individuals  and  on  the  umbonal  half  of  older  specimens. 
Large  individuals  are  almost  rayless. 

This  species  has  been  previously  known  only  from  the  Wabash  River  in 
Illinois  (Baker,  1906:77)  and  the  present  records,  although  in  the  same 
drainage  basin,  extend  the  range  of  its  distribution. 

9.  Pleurobema  coccineum  (Conrad).    Thin  Niggerhead. 

The  shell  known  as  coccineum  attains  large  size  in  certain  parts  of  the 
Salt  Fork.  It  is  common,  however,  only  at  one  place,  below  the  dam  at 
Homer  P^rk.  No  shells  of  this  species  were  observed  above  the  station 
called  bench  mark  655,  which  is  about  15  miles  below  Urbana.  The  shells 
from  habitats  above  the  dam  at  Homer  Park  exhibit  evidence  of  an  un- 
favorable environment,  the  shells  having  heavy  lines  of  growth  which  on 
some  specimens  are  raised  to  form  ridges.  These  are  especially  marked  at 
the  rest  periods  (seasonal).  The  individuals  from  the  upper  part  of  the 
stream  are  also  more  or  less  pathologic,  50  per  cent  of  the  shells  being 
abnormal  in  form  or  with  pearly  growths  on  the  inside  of  the  valves. 
Coccineum  is  found  on  both  a  mud  and  a  sand-gravel  bottom. 

There  is  considerable  variation  in  the  outline  and  general  shape  of  the 
shells  from  Salt  Fork.  The  outline  varies  from  quadrate  to  roundly  ovate 
and  the  ventral  margin  from  nearly  straight  to  strongly  convex.  Young 
and  half-grown  shells  seem  more  uniform  than  large  adult  shells.  The 
quadrate  individuals  may  easily  be  confounded  with  Fusconaia  ruhiginosa. 
In  the  last  species,  however,  the  shell  is  more  inflated  {coccineum  is  com- 
pressed), the  umbones  are  directed  upward  and  not  backward,  as  in 
coccineum,  and  the  posterior  portion  of  the  shell  has  a  depressed  area  and 
a  strong  ridge  which  are  absent  in  coccineum.  The  nacre  of  coccineum  is 
pink  of  various  shades,  only  two  specimens  from  the  Salt  Fork  having 
white  nacre.  In  this  respect  the  coccineum  of  the  Big  Vermilion  drainage 
differ  almost  constantly  from  ruhiginosa  which  has  white  nacre.  The 
epidermis  in  specimens  from  the  upper  part  of  the  stream  (Homer  Park  and 
above)  is  usually  very  dark  brown  with  faint  evidences  of  rays.  In  some 
specimens,  especially  from  the  station  three  and  a  half  miles  above  Homer 
Park  dam,  the  whole  shell,  inside  and  outside,  is  of  a  delicate  pink  shade. 
Individuals  from  the  Middle  Fork  and  the  Big  Vermilion,  where  the  species 
is  rare,  are  lighter  in  color.  The  two  largest  specimens  collected  from  the 
Big  Vermilion  drainage  measure  as  follows: 

Length,  96;  height,  75  mm.    Quadrate  form  above  Homer  dam,  Z11114  A. 
"      96        "      80  mm.     Rounded  form,  Homer  Park,  Z11164  A. 


38  ILLINOIS  BJOLOGICAL  MONOGRAPHS  [136 

In  the  Sangamon  River  coccineum  is  a  most  abundant  and  variable 
mussel,  having  a  smooth,  polished  shell  on  which  the  rays  are  many  and 
distinct.  It  also  attains  a  large  size,  though  not  as  large  as  specimens 
from  the  Big  Vermilion  drainage.  The  shape  of  the  shell  is  more  oblique 
and  eliptical  than  is  the  species  as  it  occurs  in  the  Big  Vermilion  and  the 
shell  is  a  trifle  more  inflated  on  the  average.  So  marked  is  the  difference 
that  it  is  comparatively  easy  to  say  from  the  shape  of  the  shell  and  the 
surface  markings  what  drainage  a  particular  individual  may  have  come 
from.  The  twelve  sets  of  coccineum  in  this  collection  indicate  in  a  marked 
degree  the  fact  that  species  may  differ  conspicuously  in  both  sculpture 
and  form  in  different  river  systems.  The  nacre  of  the  Sangamon  River 
coccineum  is  more  often  white  than  in  the  Big  Vermilion  shells.  Pearly 
secretions  or  pathologic  malformations  have  not  been  observed  in  the 
specimens  from  the  Sangamon  River,  indicating,  without  doubt,  a  more 
favorable  environment  than  is  provided  by  the  waters  of  the  Salt  Fork. 
Young  specimens  (25-30  mm.  long)  are  more  abundant  in  the  Sangamon 
River  than  in  the  Big  Vermilion  River,  and  these  individuals  are  beautifully 
marked  with  dark  green  rays  on  a  yellowish  or  light  brown  background. 
Occasional  shells  are  pinkish.  The  beak  markings  on  the  umbones  are 
especially  well  preserved  in  these  young  specimens. 

A  large  right  valve  from  Mahomet  is  very  peculiar.  In  outline  it  is 
ovate,  a  trifle  oblique.  The  posteroir  portion  of  the  valve  is  much  elongated 
the  hinge  line  is  long  and  straight,  and  the  posterior  margin  is  sharply, 
obliquely  truncated.  The  umbonal  region  is  near  the  anterior  margin  of 
the  valve.  The  lateral  tooth  is  longer  and  straighter  than  in  normal 
coccineum.  The  shell  recalls  Pleurobema  clava  but  is  much  larger  and 
differently  shaped.  The  valve  measures  as  follows:  length  92,  height 
70  mm. 

Ortmann  (1918:549)  considers  coccineum  a  variety  or  race  of  obliquum 
(Conrad),  together  with  solidus(  =  caiillus  Conrad),  which  is  also  rated  as 
a  variety  of  obliquum.  To  this  disposition  the  writer  cannot  agree,  the 
forms  here  listed  as  varieties  being  quite  as  much  entitled  to  specific  rank 
as  are  many  other  forms  recognized  as  distinct  species  which  have  marked 
variation  and  a  similar  facies.  The  whole  group  of  obliquum- solidum- 
coccineum  are  closely  related,  but  I  have  seen  no  good  reason  after 
examining  a  large  series  in  the  Hinkley  and  other  collections  in  the 
Museum  collections,  for  lumping  these  species  as  varieties  of  obliquum. 
As  far  as  Illinois  specimens  of  obliquum  and  coccineum  are  concerned,  the 
two  species  seem  sufficiently  distinct  for  recognition. 

10.  Rotundaria  tuberciilata  Rafinesque.    Purple  Warty-Back. 

This  species  was  found  at  but  two  places  in  Salt  Fork,  at  Homer  Park 
and  South  of  Muncie,  and  ia  the  Big  Vermilion  below  Middle  Fork.    At 


1371  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  39 

the  first  two  places  it  is  very  rare,  only  a  few  individuals  having  been 
found  by  Professor  Smith  in  a  number  of  years.  In  a  days  search  at 
Homer  Park  by  two  experienced  collectors,  only  two  living  specimens  and 
odd  valves  of  two  others  were  found.  The  largest  specimen  from  Homer 
Park  measures  72  mm.  in  length  and  63  mm.  in  height.  This  species  is  one 
of  the  most  abundant  of  shells  in  the  Big  Vermilion  below  Middle  Fork, 
where  specimens  measuring  100  mm.  in  length  are  common.  The  distri- 
bution of  this  species  is  a  good  example  of  the  progressive  development  of  a 
species  in  the  downward  course  of  a  stream,  for  in  the  course  of  about 
twenty  miles  the  size  nearly  doubles.  Beginning  as  a  rare  form  at  Homer 
Park  it  becomes  one  of  the  most  common  forms  in  the  Big  Vermilion, 
twenty  miles  downstream. 

All  of  the  Big  Vermilion  tuberculata  are  of  the  compressed  type,  and 
the  shell  is  covered  posteriorly  and  ventrally  with  large  tear-like  pustules. 
The  anterior  third  of  the  valve  is  free  from  pustulation.  The  nacre  of  all 
shells  seen  is  rich  purple,  which  renders  the  species  valueless  for  the  button 
makers.  Tuberculata  does  not  occur  in  the  portions  of  the  Sangamon  River 
examined. 

11.  Elliptic  gibbosus  (Barnes).    Lady-Finger;  Spike. 

This  mussel  does  not  occur  in  Salt  Fork,  nor  in  any  tributaries  of  the 
Big  Vermilion  above  Danville  that  have  been  examined.  It  is  fairly  com- 
mon in  the  Sangamon  River  at  Mahomet  on  a  sand  and  gravel  bottom. 
Young  and  immature  shells  are  distinctly  rayed.  The  nacre  of  all  speci- 
mens examined  has  been  purple,  no  white-nacred  individuals  being  seen. 
In  the  Kankakee  River  white-nacred  specimens  occur  and  become  the 
dominant  form  in  the  lower  part  of  the  stream  (Wilson  and  Clark,  1912 :45). 
In  the  Illinois  River  beds  of  shells  occur  which  have  either  a  white  or  a  pur- 
ple interior.  (Danglade,  1914:42).  This  familiar  shell  will  probably  have 
to  be  known  as  dilatatus  (Rafinesque)  if  the  original  description  is  definite 
enough  to  identify  it  as  the  gibbosus  of  Barnes.  Dilatatus  was  described 
in  1820.  It  is  a  pity  that  these  names  of  Rafinesque  could  not  have  been 
applied  earlier  to  these  shells  and  thus  saved  the  confusion  which  is  now 
resulting  from  the  changes  of  the  old  familiar  names  which  zoologists  in 
our  universities  have  used  for  years  in  connection  with  their  classes  in 
systematic  zoology. 

12.  Unlomerus  tetralasmus  (Say). 

This  species  has  been  found  living  only  in  the  upper  waters  of  Salt 
Fork  and  in  Stony  Brook  near  Muncie.  It  occurs  in  fair  numbers  in  the 
stream  above  Urbana  and  in  Spoon  River.  Two  broken  valves  were  found 
in  Salt  Fork  at  the  station  called  natural  dam  about  12  miles  below  Urbana. 
No  living  mussels  could  be  found  in  the  stream  at  this  point  and  it  is 
believed  that  the  odd  valves  were  washed  into  Salt  Fork  from  a  small 


40  JLUNOIS  BIOLOGICAL  MONOGRAPHS  [138 

tributary  nearby  which  was  dry  at  the  time  of  our  examination.  TetraiaS" 
mus  is  a  species  of  the  small,  mud-bottom  tributaries  and  seems  not  to 
occur  in  the  larger  part  of  the  stream  with  the  larger  and  heavier  mussels. 
The  largest  specimen  collected  measures  55  mm.  in  length.  The  colors  of 
the  shells  are  yellow,  black,  and  greenish,  the  latter  in  indistinct  ray-form. 

12a.  Uniomerus  tetralasmos  sayi  (Ward). 

Among  the  Anodontas  collected  in  Crystal  Lake  is  a  specimen  of  the 
shell  known  as  variety  sayi.  It  is  large  for  the  species  but  seems  otherwise 
typical.  The  dimensions  are:  length,  123;  height,  58;  breadth,  38  mm. 
(No.  Z  11369).  As  only  tetralasmus  is  foimd  in  the  Salt  Fork  and  its 
tributaries  it  is  probable  that  this  form  was  introduced  with  the  Anodontas 
described  on  a  subsequent  page. 

13.  StrophitQS  edentulus  (Say).    Squaw-Foot. 

This  mussel  once  occurred  in  nearly  all  parts  of  the  Big  Vermilion  River 
but  it  is  now  found  in  any  number  only  below  the  dam  at  Homer  Park. 
No  living  specimens  were  found  above  a  point  four  miles  above  Homer 
Park  dam  or  22  miles  below  Urbana.  It  occurs,  rarely,  living,  in  Spoon 
River  and  its  absence  in  a  living  state  for  a  distance  of  12  miles  between 
this  tributary  and  the  first  habitat  in  which  it  was  found  alive  in  Salt 
Fork  is  striking  and  suggestive  of  the  harmful  eJBFect  of  sewage  pollution. 
This  species  reaches  its  greatest  perfection  below  the  dam  at  Homer  Park 
on  a  gravel  bottom.  Edentulus  also  occurs  in  the  Sangamon  River,  but 
the  individuals  from  that  stream  are  not  as  large  and  are  more  compressed 
than  the  specimens  from  Salt  Fork,  which  are  as  a  rule  quite  corpulent. 
It  is  also  not  as  abundant  in  the  Sangamon  as  in  the  Big  Vermilion.  Meas- 
urements are  given  below  of  the  largest  specimens  from  the  Salt  Fork  and 
the  Sangamon. 

Length,  90;  height,  54;  width,  41  mm.    Salt  Fork,  Z11174. 
"      89        "      57      "        32  mm.    Sangamon,  Zl  1227  A. 

There  is  great  variation  among  the  shells  referred  to  this  species. 
Typical  edentulus  is  rhomboid  in  form,  rather  inflated,  with  prominent, 
inflated  umbones;  the  posterior  margin  of  the  shell  is  usually  sharply, 
obliquely  truncated,  and  the  ventral  margin  is  straight  or  even  slightly 
convex.  The  color  is  usually  black  without  rays.  From  this  type  the  shell 
varies  to  an  ovate  or  elliptical  outline,  a  more  or  less  compressed  form,  with 
a  rounded,  convex  ventral  margin  and  with  an  almost  total  absence  of  the 
strong  posterior  ridge  so  characteristic  of  the  usual  form.  The  variadon  is, 
as  would  be  expected,  toward  the  variety  known  as  pavonius.  The  shells 
from  Salt  Fork  are  very  thick  and  solid,  much  more  so  than  in  specimens 
from  the  Sangamon  River.  The  nacre  of  the  majority  of  specimens  is 
yeUowish  in  color. 


139]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  41 

13a.  Strophhus  edentulus  pavonius  (Lea). 

This  variety  is  described  by  Simpson  (1914:348)  as  "Shell  generally  long 
elliptical;  epidermis  yellowish-green,  more  or  less  covered  with  green  or 
brownish-green  rays."  In  its  typical  form  pavonius  is  easily  separable 
from  edentulus.  The  variety  is  almost  as  common  in  Salt  Fork  as  is  the 
typical  form  and  there  are  many  intermediate  individuals.  It  is  possible, 
however,  to  separate  all  of  the  edentulus  from  the  different  stations,  17  lots, 
into  two  groups;  one  with  rhomboid  or  long-ovate  outline  and  with  black 
or  brownish,  rayless  surface;  and  the  other  with  long-elliptical  outline, 
brownish  surface,  and  many  distinct  rays.  In  pavonius  the  height  is  less 
as  compared  with  the  length  than  in  edentulus.  These  two  forms  of 
Strophitus  were  almost  always  associated  together,  indicating  their  close 
relationship.  On  the  whole  pavonius  is  much  less  variable  than  typical 
edentulus.  Specimens  from  the  Sangamon  River  at  Mahomet  are  brilliantly 
rayed  with  patches  of  bright  green  on  the  ventral  margin  of  the  shell. 

Wilson  and  Clark  (1912:48)  state  that  the  "question  of  rays  appears 
to  be  closely  related  to  clearness  of  water;  in  turbid  streams  mussels  are 
usually  dull  colored,  while  in  clear  streams  they  are  usually  brightly 
rayed."  This  has  been  our  observation  in  many  cases,  but  the  rayed 
pavonius  in  Salt  Fork  occurs  with  the  rayless  edentulus  in  quiet  water 
on  a  mud  bottom;  both  also  occur  in  riffles  on  a  sand-gravel  bottom. 

Pavonius  is  credited  by  Simpson  to  Ohio  and  Indiana;  it  is  probably 
widely  distributed  in  Illinois,  but  has  most  likely  been  listed  under  edentu- 
lus in  most  cases.  It  is  known  from  Cook  County,  Will  County,  and  the 
Wabash  River  (Baker,  1906:72).  Its  presence  in  the  Sangamon  River 
indicates  that  it  is  also  an  inhabitant  of  the  Mississippi  River  drainage, 
as  well  as  the  Wabash  and  Ohio  drainages.  It  is  quite  probable  that  the 
distribution  of  the  variety  is  coincident  with  that  of  edentulus.  The  nacre 
of  both  edentulus  and  pavonius  is  usually  yellowish  or  salmon  colored  al- 
though white-nacred  specimens  occur.  Pearly  growths  are  not  as  common 
among  the  shells  of  this  species  as  found  in  the  region  under  consideration 
as  among  the  same  species  from  other  places.  A  few  individuals  had  blister 
and  pin-head  pearls.  A  specimen  each  of  the  type  and  the  variety  had  a 
peculiar  pearl  formation  on  the  pallial  line  at  or  near  the  posterior  end  of 
the  shell.  These  are  somewhat  dome-shaped,  about  5  mm.  in  diameter 
and  4  mm.  in  height  and  evidently  were  caused  by  an  effort  on  the  part  of 
the  moUusk  to  cover  some  irritating  object,  possibly  a  nematode  worm 
(Figs.  31,  32).  As  both  shells  were  without  the  animal  {pavonius  had 
been  alive  very  recently)  this  point  could  not  be  determined.  The 
edentulus  was  from  the  railroad  bridge  east  of  Sidney  (No.  Z11098)  and 
the  pavonius  from  below  Homer  Park  dam  (No.  Z11144  A). 


42  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [140 

14.  Anodonta  grandis  Say.    Floater. 

The  floater  or  paper-shell  is  more  or  less  abundant  in  Salt  Fork  and 
other  parts  of  the  Big  Vermilion  drainage.  In  Spoon  River  it  is  common, 
living  in  the  lower  part  of  the  stream.  From  this  station  to  the  station 
called  bench  mark  655,  over  five  miles  below,  not  a  living  Anodonta  could 
be  found,  and  the  species  does  not  become  abundant  until  the  cement 
bridge  east  of  Sidney  is  reached,  nine  miles  below  Spoon  River.  This 
distribution  is  again  indicative  of  the  harmful  influence  of  sewage  on  the 
bottom  inhabiting  animals.  From  the  cement  bridge  to  the  Homer  Park 
dam  grandis  is  fairly  common.  It  was  very  rare  below  the  station  at  Homer 
Park,  at  which  place  it  is  common.  The  best  habitat  observed  appears 
to  be  between  the  cement  and  railroad  bridges  east  of  Sidney,  where  the 
water  is  fairly  deep  in  summer  (three-four  feet)  and  where  there  is  a  soft 
mud  bottom  and  not  much  of  a  current  in  the  stream.  The  species  is 
t)rpically  a  pond-inhabiting  mussel.  Gravid  individuals  were  collected  on 
September  13,  1918. 

At  Mahomet,  on  the  Sangamon  River,  grandis  is  abundant  and  of  large 
size,  and  occurs  on  a  fine  sand  bottom.  The  Sangamon  specimens  are 
on  the  whole  more  cylindrical  in  form  than  those  from  the  Big  Vermilion 
and  have  a  brown  or  brownish-green  epidermis.  The  Big  Vermilion 
specimens  are  mostly  grass-green  in  color  and  are  more  elongate-ovate 
in  form,  the  ventral  margin  being  almost  universally  rounded  while  in  the 
Sangamon  shells  this  margin  is  nearly  straight.  The  Sangamon  River 
grandis  are  on  the  whole  more  solid  than  the  same  species  from  Salt  Fork. 

The  nacre  of  the  great  majority  of  the  Salt  Fork  specimens  is  bluish- 
white,  while  that  of  the  Sangamon  specimens  is  salmon-colored  for  the 
most  part.  A  few  individuals  from  both  streams  have  salmon-colored 
patches  and  small  pearl  growths  indicating  that  the  animals  had  suffered 
from  the  attack  of  distomid  worms,  possibly  the  distomid  of  Osborn,  which 
is  known  to  infest  this  species  in  other  places  (Wilson  and  Clark,  1912). 
These  shells,  however,  were  rare  and  infection  from  this  source  seem 
uncommon  among  the  grandis  of  these  streams.  No  Unionicola  {Atax) 
or  other  water-mites  were  observed  in  this  species.  These  parasites  are 
common  in  grandis  inhabiting  other  streams  (Wilson  and  Clark,  1912: 
61-71). 

An  empty  shell  from  the  big  bend  in  the  Salt  Fork  showed  evidences 
of  distomid  infection  in  the  form  of  elongated  blisters  on  the  ventral 
margin  of  the  valves,  near  the  pallial  line.  In  the  right  valve,  near  the 
anterior  adductor  muscle  scar,  there  is  a  large  blister,  8  by  12  mm.  which 
evidently  covered  a  distomid.  The  left  valve  of  this  specimen  had  suf- 
fered an  injury  when  the  animal  was  about  two-thirds  grown,  which  has 
caused  a  part  of  the  an tero- ventral  margin  to  become  folded  inward,  a  part 
of  the  folded  portion  having  the  epidermis  well  preserved.    The  animal 


i 


141]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  43 

continued  its  shell  formation  so  perfectly  that  from  the  outside  no  evidence 
of  an  injury  is  visible.  This  shell  indicates  plainly  a  case  of  a  hard  struggle 
for  existence  against  both  mechanical  injury  and  heavy  parasitism.  The 
interior  of  the  shell  is  spotted  with  grayish  patches  and  salmon-colored 
streaks  (No.  Z11029-A).    (Figs.  22,23.) 

14a.    Anodonta  grandis  gigantea  Lea.    Floater. 

Specimens  of  an  Anodonta  from  Crystal  Lake,  Urbana,  are  apparently 
referable  to  Lea's  gigantea.  Simpson  (1914:420)  diagnoses  this  variety 
as  "Shell  large,  ovate  or  subrhomboid,  a  little  higher  in  proportion  to  the 
length  than  the  type;  beaks  full  and  high."  The  specimens  from  Crystal 
Lake  agree  with  this  diagnosis.  The  largest  individual  measures  152  mm. 
in  length  and  92  mm.  in  height.  The  umbonal  region  is  more  corpulent 
than  in  the  grandis  from  the  other  parts  of  the  Salt  Fork.  The  color 
is  brownish  or  greenish,  the  two  colors  frequently  in  alternating  zones 
on  the  same  specimen.  Evidences  of  distomid  infection  are  common  in  the 
form  of  salmon  or  pink  discolorations  and  ridges.  One  individual  has  many 
long,  thin,  curved  ridges  on  the  interior  of  the  shell,  principally  in  the  left 
valve.  One  of  these  ridges  measures  93  mm.  in  length  and  1 .  50  mm.  in 
height  (Fig.  24).  Another  individual  has  a  round  pearl  attached  to 
the  posterior  end  of  the  shell,  measuring  5  mm.  in  diameter.  This  variety 
has  not  been  observed  in  any  collections  from  the  Big  Vermilion  or  Sanga- 
mon rivers.  Marsh  has  recorded  gigantea  from  the  Big  Vermilion  (Baker, 
1906:73)  but  the  exact  location  is  not  known,  and  must  have  been  below 
the  points  examined  by  the  writer. 

15.  Anodonta  corpulenta  Cooper.    Floater. 

The  large  Anodontas  from  Crystal  Lake  are  divisible  into  two  groups; 
one  is  the  variety  of  grandis  described  above;  the  other  seems  to  be  the 
corpulenta  of  Cooper,  although  the  shells  are  smaller  than  examples  of 
this  species  from  other  rivers.  The  shells  referred  to  corpulenta  are  sub- 
rhomboid,  somewhat  elongated  in  a  few  of  the  individuals.  The  umbonal 
swelling  is  very  pronounced,  extending  well  downward  on  the  shell.  The 
anterior  end  is  broadly  rounded  and  the  posterior  end  is  distinctly  plow- 
shaped  and  rather  strongly  biangulate.  The  epidermis  is  olive  or  brownish. 
The  surface  is  very  rough,  the  growth  lines  in  some  specimens  being 
elevated  into  longitudinal  ridges.  As  in  gigantea,  the  inner  surface  is 
ridged  and  salmon-colored  in  many  specimens  due  to  the  presence  of 
distomid  worms.  No  specimens  of  this  species  were  seen  which  did  not  in 
some  degree  show  evidences  of  the  work  of  this  parasite.  Characteristic 
measurements  of  this  shell  are  given  below  (Z11368): 

Length,  127;  height,  82;  breadth,  Si  mm. 
"       119        "      71  "       58  mm. 

"       128        "      70  *'       50  mm. 

"       HI        "      64  "       50  mm. 


44  ILLINOIS  BIOLOGICAL  MONOGRAPHS  (142 

The  large  Anodontas  in  Crystal  Lake  are  apparently  not  members  of 
the  original  Salt  Fork  fauna.  Neither  grandis  gigantea  or  corpulenta  are 
found  anywhere  in  the  Big  Vermilion  drainage,  at  least  above  Middle  Fork, 

45  miles  below  Urbana.  Since  these  shells  were  planted  in  the  lake  (see 
p.  27)  they  have  evidently  thrived  and  multiplied.  Anodonta  grandis  foot- 
iana  is  parasitic  in  the  glochidial  stage  on  the  Johnny  Darters  (Boleosoma 
nigrum,  Hankinson,  1908:235)  and  as  this  fish  also  inhabits  Crystal  Lake 
it  may  have  been  the  medium  for  the  propagation  of  the  alien  fauna.  That 
this  fauna  should  have  been  so  easily  detected  as  alien  is  due  to  the  method 
of  examining  a  stream  from  its  source  to  its  mouth  and  the  distinguishing 
of  the  foreign  population  is  a  striking  recommendation  of  this  mode  of 
stream  study. 

16.  Anodonta  imbecilHs  Say.    Paper-Shell. 

This  beautiful  paper-shell  occurs  abundantly  in  but  one  place  in  the 
Salt  Fork — near  the  cement  bridge  east  of  Sidney.  Here  it  is  of  good  size, 
grass-green  in  color,  the  rest  periods  showing  as  black  longitudinal  bands. 
The  shell  is  easily  known  from  all  others  in  this  State  by  the  very  flat 
umbonal  region  which  is  flush  with  the  upper  or  dorsal  margin  of  the  shell. 
The  largest  specimen  in  the  collection  measures  75  mm.  in  length.  Imbe- 
cilHs was  not  collected  or  observed  above  the  cement  bridge,  19  miles  down 
stream  from  Urbana.  It  was,  also,  not  seen  below  the  bed  at  Homer  Park 
and  it  appears  to  inhabit  only  that  portion  of  the  stream  between  these 
points,  a  distance  of  about  8  miles.  This  mussel  thrives  best  on  a  mud  bot- 
tom in  quiet  water  and  it  is  not  found,  normally,  on  a  sand  or  gravel  bottom. 
It  did  not  occur  in  our  Sangamon  River  collections. 

All  of  the  individuals  from  Salt  Fork  bear  evidences  of  distomid  infec- 
tion. In  nearly  all  of  the  valves  there  are  many  small  pearl-like  blisters 
about  the  size  of  a  pin  head  which  are  in  all  cases  confined  to  the  posterior 
two-thirds  of  the  shell.    None  were  noted  near  the  anterior  end. 

The  species  is  peculiar  and  almost  unique  among  naiades  in  being 
hermaphroditic  and  in  carrying  the  glochidia  within  the  gills  until  they  are 
ready  for  independent  life,  there  being  no  parasitic  stage  encysted  on  fish 
as  in  the  case  of  most  Unionidae  (Howard,  1914:353).  It  has  an  almost 
continuous  breeding  season,  glochidia  or  embryos  having  been  found  in 
the  gills  during  almost  every  month  of  the  year.  The  Salt  Fork  specimens 
were  gravid  on  August  26  and  contained  well  formed  glochidia.  In  this 
mode  of  reproduction  imbecillis  is  parallelled  by  Strophitus  edentidus, 
which  also  passes  through  its  metamorphosis  without  parasitism. 

17.  Anodontoides  ferussacianus  (Lea).    Paper-Shell. 

This  small  naiad  was  found  abundantly  in  but  two  places — the  Middle 
Fork  and  Stony  Creek  near  Muncie.  It  occurred  infrequenty  at  all  other 
stations.    In  the  upper  Salt  Fork,  north  of  Urbana,  it  was  common  at  one 


143]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  45 

time,  near  Lincoln  Avenue,  and  in  Crystal  Lake.  Two  summers  collecting 
failed  to  find  it  common  at  the  present  time  at  these  places.  Living  speci- 
mens were  not  found  in  the  Salt  Fork  betwen  Spoon  River  and  the  big 
bend  below  the  natural  dam,  a  distance  of  over  four  miles,  and  it  did  not 
occur  even  infrequently  above  Homer  Park  dam,  a  distance  of  17  miles. 

All  of  the  specimens  collected  are  fresh,  bright  colored  shells,  greenish 
or  olive  with  distinct  grass-green  rays.  All  but  one  specimen  were  normal  in 
form  and  coloration.  An  individual  from  the  cement  bridge  station  was 
thicker  than  usual,  had  a  short  truncated  posterior  end  and  somewhat 
resembled  small  specimens  of  Strophitus  edentulus.  The  beak  sculpture  was 
characteristic  of  Anodontoides.  Pearly  growths  and  abnormalities  are 
rare  in  the  shells  collected.  Gravid  females  were  found  September  26  and 
October  8.  It  seems  to  be  rare  in  the  Sangamon  River,  only  a  stray  valve 
being  found  in  this  river  near  White  Heath. 

17a.  Anodontoides  ferussacianus  buchanensis  (Lea). 

Specimens  from  the  Salt  Fork  near  Muncie  and  from  the  Big  Vermilion 
are  referable  to  this  variety,  long  known  under  the  name  subcylindracea 
of  Lea.  The  variety  in  the  Big  Vermilion  drainage  is  more  elongate,  more 
cylindrical,  and  has  a  less  height  in  comparison  with  the  length  than  in  the 
typical  form.  It  is  also  decidedly  biangulate  behind,  a  characteristic  lack- 
ing in  the  typical  form.  At  the  two  localities  it  is  associated  with,  ferussacia- 
nus, but  at  Muncie  it  is  the  prevailing  form. 

18.  Arcidens  confragosus  (Say).    Rock-Shell. 

This  species  is  a  rare  inhabitant  of  the  Sangamon  River  and  is  not  found 
in  the  Big  Vermilion  River.  It  was  reported  from  the  Sangamon  River  at 
White  Heath  and  Monticello  by  Mr.  James  Zetek,  about  ten  years  ago. 
Professor  Smith  has  not  found  it  at  Mahomet  during  many  years  of  col- 
lecting. Recently  (September  1920)  a  single  specimen,  dead,  was  picked 
up  by  the  writer  in  the  Sangamon  River  at  a  point  about  four  miles  above 
Mahomet,  thus  establishing  its  presence  above  White  Heath.  It  probably 
lives  sparingly  in  the  river  and  may  inhabit  water  too  deep  for  examination. 
It  has  been  reported  from  the  Sangamon  at  Springfield  (Baker,  1906:74). 

19.  Lasmigona  (Platynaias)  compressa  (Lea). 

This  characteristic  species  is  rare  in  the  Big  Vermilion  River.  Several 
fine  specimens  were  collected  from  the  station  three  and  a  half  miles  above 
Homer  Park  in  riffles  on  a  sand-gravel  bottom.  One  of  these  shells  is 
pathologic,  the  umbones  being  almost  in  the  center  of  the  shell,  the  anterior 
end  having  a  strong  depression  in  front  of  the  umbones.  The  posterior 
end  is  much  shorter  than  usual  and  is  rounded  instead  of  broadly  truncate. 
The  interior  shows  distomid  parasitism  near  the  posterior  end  with  a  large 
elongated  blister  near  the  postero-ventral  margin.    The  pseudocardinal  in 


46  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [144 

the  right  valve  is  elongated  and  thinner  than  in  normal  individuals  and 
the  lateral  teeth  in  both  valves  are  scarcely  visible.  In  the  left  valve  there 
is  an  abnormally  high,  long  and  narrow  tooth  imder  the  beak.  There  is 
a  pronounced  lunule  in  front  of  the  umbones  which  is  absent  in  typical 
compressa.  This  species  occurs  infrequently  in  mud  at  Homer  Park.  In 
the  Middle  Fork  a  single  dead  and  broken  shell  was  found.  No  represen- 
tatives of  this  si>ecies  were  foimd  in  the  Sangamon  River. 

20.  Lasmigona  (Lasmigona)  costata  Rafinesque.    Fluted  Shell. 

This  characteristic  mussel  is  fairly  common  at  most  stations  vdsited 
from  bench  mark  655  (fifteen  miles  below  Urbana)  down  the  stream  to 
Middle  Fork.  It  probably  inhabits  the  lower  Big  Vermilion  to  the  Wabash 
River.  Living  specimens,  however,  were  not  seen  above  the  station  four 
miles  above  Homer  Park  dam,  nearly  23  miles  from  Urbana.  From  Homer 
Park  down  stream  it  is  a  common  mussel.  The  individuals  are  for  the  most 
part  fine,  large,  heavy  shells  with  good  clean  lustre.  The  shells  from  Homer 
Park  have  an  olive  epidermis  beautifully  marked  with  green  rays.  The 
largest  individual  collected  measured  145  mm.  in  length  and  was  foimd  at 
the  station  three  and  a  half  miles  above  Homer  Park  dam  (Z11116A). 

The  majority  of  the  specimens  of  this  species  are  colored  light  salmon 
on  the  interior  of  the  shell.  Pathological  individuals  are  rare  in  the  collec- 
tions. One  specimen  from  Salt  Fork  near  Middle  Fork,  found  on  a  sand 
bottom,  has  a  large  pearl  blister  on  the  posterior  margin.  A  shell  from 
Homer  Park,  taken  from  a  gravel  bottom,  has  an  injury  in  the  form  of  a 
crack  in  the  shell  on  the  outside  which  had  been  repaired  on  the  inside  by 
the  addition  of  pearly  matter  forming  a  long,  raised  blister,  45  mm.  long 
and  2  to  5  mm.  wide  (Fig.  33).  This  nodulous  blister  reaches  almost 
to  the  center  of  the  shell  (Z11192  A).  Gravid  individuals  were  collected  on 
October  8  and  13,  1920. 

The  costata  from  the  Sangamon  River,  where  the  species  is  common, 
are  somewhat  heavier  than  those  from  the  Big  Vermilion  River.  The 
shell  is  ^so  less  high  in  comparison  with  its  length.  Yoimg  individuals  of 
this  species  from  either  river  drainage  are  very  rare,  judging  by  our  collec- 
tions. 

21.  Lasmigona  (Ptcrosygna)  complanata  (Barnes).    White  Heel-Splitter. 
This  large,  roimdish,  flat  mussel  is  the  most  abimdant  species  in  the 

Big  Vermilion  River,  occurring  commonly  or  abundantly  in  all  parts  of  the 
stream,  excepting  a  small  stretch  of  about  five  miles  near  St.  Joseph,  from 
Spoon  River  to  the  neighborhood  of  Danville.  It  also  probably  occurs  in 
equal  abundance  below  DanviUe.  The  abundance  of  this  species  in  Spoon 
River  and  below  the  station  bench  mark  655,  with  the  break  of  five  miles 
between  the  beds  of  living  mussels,  is  strong  evidence  of  the  effect  of  sewage 
pollution.    In  this  barren  area  only  empty  shells  and  odd  valves  could  be 


145]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  47 

found  after  careful  search;  in  one  place,  below  the  first  bridge  south  of  St. 
Joseph,  dead,  empty  shells  were  abundant,  but  a  careful  search,  conducted 
on  two  days,  failed  to  discover  a  single  living  specimen.  The  largest  and 
finest  shells  occur  at  Homer  Park  on  a  mud  bottom  in  water  from  two  to 
three  feet  deep.  The  largest  shell  from  this  station,  a  female,  measured: 
length,  185;  height,  130  mm.  The  species  was  observed  to  be  gravid  on 
the  6th  of  November,  in  1918,  and  on  October  8,  in  1920. 

The  shells  of  complanata  are  very  uniform  in  general  shape,  nacre,  and 
condition.  Pearly  growths  or  pathological  forms  are  rare.  A  few  specimens 
contained  small  pin-head  pearls  and  an  occasional  individual  had  suffered 
slight  injury  to  the  posterior  part  of  the  shell.  The  presence  of  many  young 
and  immature  specimens  indicates  that  the  species  is  now  breeding  well 
and  that  the  glochidia  are  finding  suitable  fish  hosts.  Young  shells  from  the 
Sangamon  River,  where  the  species  is  abundant,  are  more  of  an  olive  color 
and  not  as  green  as  those  from  the  Salt  Fork  and  other  parts  of  the  Big 
Vermilion  River.    Old  shells  from  both  drainages  are  dark  brown  or  black, 

22.  Alasmidonta  (Pressodonta)  calceola  (Lea). 

This  species  has  been  recorded  by  Mr.  Zetek  from  west  of  White  Heath 
in  the  Sangamon  River.  No  specimens  were  observed  during  the  recent 
survey.    As  far  as  known  it  does  not  occur  in  the  Big  Vermilion  River. 

23.  Alasmidonta  (Rugifera)  marginata  Say.    Elk-Toe. 

In  the  big  Vermilion  River,  this  species  is  found,  infrequently,  at  most 
stations  from  bench  mark  655  as  far  down  as  the  stream  has  been  examined. 
It  is  not  abundant  anywhere  and  common  at  but  three  stations — below 
the  dam  at  Homer  Park,  south  of  Muncie,  and  in  the  Big  Vermilion.  The 
first  station  where  living  specimens  were  found  is  four  miles  above  the 
Homer  Park  dam.  Individuals,  both  above  and  below  the  dam,  are  of 
good  size  and  fine  color,  the  characteristic  green  rays  being  very  brilliant. 
Specimens  from  Middle  Fork  have  many  black  spots  on  the  shell.  The 
largest  specimen  collected  from  the  station  two  miles  above  the  Homer  dam, 
measured  80  mm.  in  length  and  45  mm.  in  height;  one  from  the  Big  Vermil- 
ion measured  96  mm.  in  length  and  48  mm.  in  height. 

Marginata  exhibits  little  evidence  of  parasitism  or  abnormalities.  One 
specimen  collected  from  two  miles  above  the  Homer  dam  had  several 
pearly  growths  and  blisters  indicating  distomid  infection.  Gravid  females 
were  collected  on  October  8  and  13,  1920. 

This  species  is  rare  in  the  Sangamon  River,  only  one  specimen  being 
found  at  Mahomet  during  a  days  search.  Marginata  is  a  species  more  com- 
mon in  the  upper  waters  of  rivers  and  streams  and  is  not,  as  a  rule,  found 
in  any  number  in  the  larger  rivers. . 


48  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [146 

24.  Amygdalonaias  elegans  (Lea) .    Deer-Toe. 

But  one  specimen  of  this  peculiar  species  was  found.  This  individual 
was  collected  by  Professor  Smith  at  the  big  bend  below  the  natural  dam. 
The  specimen  was  an  empty  shell,  iron  stained  outside  and  inside,  and 
apparently  had  not  been  living  for  a  considerable  time.  It  is  typical  in 
form  but  not  as  large  as  individuals  from  the  larger  rivers.  The  measure- 
ments of  this  specimen  are:  length,  57;  height,  47;  width,  27  mm.  That 
but  one  specimen  of  this  species  should  have  been  collected  in  this  river 
drainage  seems  quite  surprising,  indicating,  probably,  that  the  species 
has  not  been  able  to  become  established.  It  is  not  found  in  the  Sangamon 
River  as  far  as  known.  , 

25.  Obovaria  circulus  (Lea). 

This  nearly  circular  mussel  was  collected  at  but  five  stations  in  the 
Big  Vermilion  River;  Homer  Park  below  the  dam,  near  Muncie,  Salt  Fork 
near  Middle  Fork,  in  Middle  Fork,  and  in  the  Big  Vermilion  below  Middle 
Fork.  It  is  infrequent  at  the  first  place  and  abundant  only  in  Middle  Fork, 
near  its  junction  with  Salt  Fork,  on  a  gravel  and  sand  bottom,  in  fairly 
shallow  water  (September)  and  in  the  Big  Vermilion  (October).  In  the 
Big  Vermilion  this  species  is  very  uniform  in  shape  and  size,  the  ratios  of 
height  to  length  ranging  between  70  and  90  per  cent.  The  shells  are  usually 
nearly  circular  and  have  a  distinct  light  yellowish-brown  zone  at  the  pos- 
terior margin.  The  nacre  is  pearly  and  there  are  no  evidences  of  discolora- 
tion from  injury  or  parasitism.  It  has  not  been  found  in  the  Sangamon 
River. 

As  in  the  case  of  so  many  of  our  mussels  whose  names  have  become 
familiar,  this  species  may  have  to  be  changed  to  that  of  subrotunda  Rafin- 
esque  (1820). 

26.  Actlnonaias  ligamentina  (Lamarck).    Mucket. 

This  mussel  was  not  found  above  the  Homer  Park  dam.  It  occurred 
infrequently  (almost  rarely)  below  the  dam  on  both  a  mud  and  a  gravel 
bottom.  In  the  Salt  Fork  near  its  junction  with  Middle  Fork  but  one  dead 
shell  was  found  in  half  a  days  search  for  a  distance  of  nearly  a  mile  up 
stream.  In  Middle  Fork,  between  the  interurban  bridge  and  the  mouth 
of  the  stream,  it  was  fairly  common  on  a  gravel  and  fine  sand  bottom  in 
shallow  water  near  rifiles.  In  the  Big  Vermilion  below  Middle  Fork  it  is 
the  most  abundant  mussel,  attaining  a  length  of  over  135  mm. 

The  individuals  of  this  species  are  all  normal  specimens;  the  young  and 
half-grown  shells  are  greenish  with  many  dark  green  rays  of  various  width. 
Older  shells  are  yellowish  with  few  rays.  In  an  old  shell  measuring  120  mm. 
in  length  and  75  mm.  in  height  the  rays  showed  but  faintly  (Z  11216). 
Evidences  of  distomid  enfection  were  rare  in  this  species  in  the  Big  Ver- 


147]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  49 

milion  specimens.  A  long  narrow  pearly  blister  on  the  posterior  margin  of 
one  specimen  might  have  been  due  to  the  presence  of  the  marginal  distomid 
described  by  Kelly.  Clark  and  Wilson  (1912:62)  found  this  distomid  com- 
mon as  cysts  in  ligamentina  from  the  Maumee  River.  A  specimen  from 
the  Big  Vermilion  had  a  large  pearl-like  blister  at  the  lower  edge  of  the 
posterior  adductor  muscle  scar.  (Z  11482  A).  An  abnormal  shell  without 
the  animal,  was  found  in  Middle  Fork,  The  posterior  end  is  sharply  trun- 
cated and  bent  inward  in  the  right  valve  and  bent  outward  in  the  left  valve. 
The  hinge  teeth  are  much  more  elevated  and  heavier  than  in  normal  speci- 
mens. This  abnormality  was  due  to  an  injury  received  when  the  shell  was 
about  three  years  old.  It  must  have  lived  upward  of  two  years  after 
receiving  the  injury,  judging  by  the  rest  marks  on  the  shell.  This  individual 
measures  length,  84,  height,  52  mm.  (Z11216A). 

The  Middle  Fork  and  Big  Vermilion  shells  are  thick  and  of  good,  clear, 
peerly- white  lustre.  The  mucket  is  one  of  the  most  valuable  shells  for  the 
cutting  of  button  blanks  and  the  Middle  Fork  and  Big  Vermilion  speci- 
mens appear  to  be  of  excellent  quality  for  this  purpose.  The  species  from 
this  stream  could  be  used  for  glochidial  infection  of  fish.  Gravid  females 
were  collected  on  September  26.  Ligamentina  was  not  found  in  the  Sanga- 
mon River. 

27.  Actinonalas  ellipsiformls  (Conrad). 

This  small  naiad  occurs  rarely  at  three  places  in  the  Big  Vermilion 
River;  below  the  dam  at  Homer  Park,  in  the  Salt  Fork  south  of  Muncie, 
and  in  the  Big  Vermilion  below  Middle  Fork.  Whether  this  rarity  is  due 
to  a  real  scarcity  of  the  mussel  or  to  the  inability  of  the  collectors  to  find  it, 
is  not  known.  Diligent  search  was  made  in  the  various  places  visited, 
and  the  fact  that  but  few  specimens  have  been  found  by  Professor  Smith 
after  years  of  constant  collecting  at  Homer  Park,  leads  to  the  conclusion 
that  the  species  is  rare  in  this  stream. 

EUipsiformis  is  common  in  the  Sangamon  River  at  Mahomet  where  it 
occurs  on  a  sand  and  gravel  bottom,  more  commonly  on  rifiies,  where  the 
current  is  rather  swift.  The  shells  from  this  station  are  not  large  (maximum 
size,  length,  63,  height,  31  mm.)  but  are  very  thick,  with  pearly- white 
nacre.  The  shape  is  normal,  the  posterior  end  being  sharply  pointed  with  a 
narrow  truncation.  The  color  is  yellowish  or  greenish  with  many  dark 
green  rays,  often  wavy.  Rest  periods  show  as  elevated  longitudinal  ridges, 
especially  near  the  ventral  margin  of  the  shell.  A  half-grown  specimen, 
length  38,  height  23  mm.,  resembles  in  outline  young  shells  of  Actinonaias 
ligamentina  and  if  found  with  that  species  would  probably  be  so  identified. 
Ligamentina,  however,  is  not  found  at  Mahomet,  and  this  specimen  is 
doubtless  referable  to  ellipsiformis.  Utterbach's  reference  of  the  species 
to  the  genus  Nephronaias  (=  Actinonaias)  is  strengthened  by  the  similarity 
of  these  shell  characters,  which  this  author  has  also  noted  (1916:  142). 


50  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [148 

In  the  largest  specimen  of  this  species,  from  the  Sangamon  River,  the 
right  valve  has  a  large  blister  parallel  with  the  postero-ventral  border, 
measuring  17  by  7  mm.,  and  anterior  to  this  blister  a  group  of  twenty  of 
more  'pin-head'  pearls.  There  are  several  of  these  small  pearls  in  the  center 
of  the  valve.  The  left  valve  has  a  number  of  *pin-head'  pearls  bordering  the 
pallial  line  and  one  larger  (1  mm.)  black  pearl  in  the  center  of  the  valve. 
(Z11230  A).  These  may  have  been  caused  by  distomid  parasites,  although 
none  were  observed  in  the  animals  of  this  species.  Onfy  one  shell  in  a  dozen 
were  thus  affected. 

28.  Gminculma  parva  (Barnes). 

This  diminutive  mussel  is  characteristic  of  the  smaller  tributaries  of 
the  Big  Vermilion  River.  It  occurs  commonly  in  the  ditch  above  Urbana 
and  also  in  Spoon  River.  No  living  specimens  were  found  between  the 
Spoon  River  tributary  and  the  station  one  mile  above  iron  bridge  north  of 
Sidney,  a  distance  of  over  six  miles.  From  this  station  to  the  railroad 
bridge  east  of  Sidney,  a  distance  of  three  miles,  this  species  was  abundant 
or  common.  It  is  infrequent  at  Homer  Park  and  was  not  found  in  the 
Salt  Fork  below  Muncie  or  in  Middle  Fork.  Its  normal  habitat  in  the  Salt 
Fork  is  on  a  mud  bottom  in  quiet  water.  At  Homer  Park,  however,  it 
occurs  sparingly  on  a  gravel  bottom  in  very  shallow  water. 

The  species  as  found  in  Salt  Fork  is  normal  in  form  but  not  of  large 
size,  the  largest  specimen  observed,  from  the  railroad  bridge  east  of  Sidney, 
measuring  30  mm.  in  length  and  18  mm.  in  height  (Z11096).  The  surface 
in  the  Salt  Fork  specimens  is  rayless,  the  color  being  brown  from  the  um- 
bones  to  the  center  of  the  valve,  the  balance  of  the  shell  being  black. 
Specimens  from  Spoon  River  were  smaller  than  those  from  farther  down 
the  stream. 

Parva  occurs  infrequently  in  the  Sangamon  River  at  Mahomet  on  a 
mud  or  sand  bottom. 

29.  Caruncullna  glans  (Lea). 

This  small  mussel,  which  is  much  higher  in  proportion  to  its  length 
than  parva,  is  very  rare  in  Salt  Fork,  where  it  was  found  at  but  three 
stations,  living  individuals  being  collected  only  below  the  dam  at  Homer 
Park.  Like  parva,  it  is  a  species  of  the  smaller  tributaries  and  its  normal 
habitat  is  on  a  mud  bottom.  It  was  not  found  in  the  Sangamon  River  at 
any  station  examined. 

Frierson  (1914:  7)  has  identified  Lea's  glans  with  the  shell  called 
Unio  (Toxolasma)  lividus  of  Rafinesque,  changing  the  generic,  name, 
accordingly,  to  Toxolasma  Rafinesque.  In  this  he  is  followed  by  Ortmann 
(1918:572,  573).  Should  these  names  be  plainly  identifiable  from  the 
original  descriptions,  these  small  shells  will  bear  the  names  Toxolasma 
parvutn  (Barnes)  and  T.  lividum  Rafinesque.    The  writer  wonders  whether 


149]  FA  UNA  OF  BIG  VERMILION  RI VER— BAKER  51 

some  of  these  Rafinesquean  names  have  not  been  adopted  too  hastily  and 
whether  the  fact  of  the  identified  specimens  in  the  Poulson  collection  has 
not  unduly  influenced  the  references,  which,  without  these  identifications, 
are  not  as  clear.  The  test  must  be,  it  would  seem,  a  clear  case  of  identifi- 
cation from  the  writings  of  Rafinesque  alone. 

30.  Eurynia  (MIcromya)  lienosa  (Conrad). 

The  distribution  of  this  small  mussel  seems  to  be  coincident  with  that  of 
Lampsilis  luteola  in  the  Big  Vermilion  and  its  tributaries.  It  occurred 
infrequently  living  in  the  Spoon  River.  It  was  not  again  collected  in  a 
living  condition  above  the  iron  bridge  north  of  Sidney,  seven  miles  below 
Spoon  River.  At  this  place  only  one  living  specimen  was  found,  and  as 
far  down  as  the  cement  bridge  it  is  only  infrequent.  Between  this  point 
and  the  station  three  and  a  half  miles  above  Homer  Park  dam  no  living 
specimens  were  found  after  diligent  search  in  favorable  habitats.  It  does 
not  occur  in  any  abundance  above  Homer  Park  dam;  but  below  the  dam 
the  species  is  abundant  and  of  large  size.  The  largest  specimens  from 
Homer  Park  measure:  length,  65;  height,  31;  breadth,  28  mm.  (male); 
length,  55;  height,  34;  breadth,  25  mm.  (female).  In  Salt  Fork  near  its 
junction  with  Middle  Fork  it  is  abundant  and  in  the  Middle  Fork  it  is 
common. 

The  species  varies  somewhat  in  coloration.  From  Homer  Park  up- 
stream the  color  is  black  or  dark  brown  with  rarely  faint  indications  of 
rays.  Specimens  from  Middle  Fork  and  Salt  Fork  near  Middle  Fork  are 
more  of  a  chestnut  color,  slightly  reddish,  often  with  quite  distinct  rays. 
By  arranging  the  different  lots  by  consecutive  stations  down  the  river  it 
may  be  at  once  observed  that  there  is  a  marked  and  striking  increase  in 
size,  the  increase  being  in  some  cases  as  much  as  50  per  cent  between  Spoon 
River  and  Homer  Park.  The  Homer  Park  shells  are  on  the  average  some- 
what larger  than  those  from  farther  down  the  stream  and  from  Middle 
Fork. 

The  shells  of  many  individuals  of  this  species  contain  pearly  growths 
in  the  form  of  blisters  and  *pin-head'  pearls.  These  occur  near  the  margin 
of  the  valve,  more  frequently  near  the  posterior  end  near  the  siphonal 
region.    Gravid  females  were  collected  at  Homer  Park  on  July  30. 

Lienosa  was  not  collected  from  the  Sangamon  River  and  no  records 
have  been  seen  of  its  occurrence  in  that  stream. 

31.  Eurynia  (Micromya)  iris  (Lea). 

A  broken  valve  of  this  species  was  found  in  Middle  Fork  below  the 
interurban  bridge.  The  rays  are  distinct  and  the  shell  seems  typical. 
It  measures,  length  37,  height  21  mm.  It  appears  to  be  a  very  rare  shell 
in  the  parts  of  the  Big  Vermilion  examined  but  may  be  more  abundant 


52  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [150 

below  the  stations  examined  where  the  river  is  larger.    Iris  has  not  been 
recorded  from  the  Sangamon  River. 

32.  Lampsilis  luteola  (Lamarck).    Fat  Mucket. 

The  mussel  known  among  fishermen  as  the  fat  mucket  is  common  or 
abundant  almost  everywhere  in  the  Big  Vermilion  and  Sangamon  rivers. 
It  has  been  killed  by  the  sewage  of  the  Salt  Fork  from  St.  Joseph  to  bench 
mark  655,  a  distance  of  five  miles  down  the  stream,  but  the  number  of  dead 
and  empty  shells  found  almost  everywhere  between  these  points  indicates 
that  at  one  time,  not  very  remote,  it  was  common  continuously  from  Spoon 
River,  where  it  now  lives  in  some  abundance,  to  the  Wabash  River.  Below 
the  dam  at  Homer  Park  it  is  very  common  and  of  large  size,  and  this  abun- 
dance continues  down  the  stream  and  was  also  noted  in  the  tributary  Mid- 
dle Fork.    At  Mahomet  on  the  Sangamon  River  it  is  also  abundant. 

There  is  great  variation  both  in  form  and  coloration  among  the  shells 
of  this  species  in  all  of  the  habitats  examined.  The  male  shells  are  usually 
pointed  at  the  posterior  end  and  are  elongated  and  somewhat  compressed. 
From  this  form  they  vary  by  being  quadrate  in  outline  with  a  distinctly 
plow-shaped  posterior  end,  corpulent  and  almost  cylindrical,  or  flattened 
and  oval,  in  this  form  greatly  resembling  Actinonaias  ligamentina,  from 
which  they  may  be  distinguished  by  the  numerous  double-looped  ridges 
on  the  umbones.  The  female  shells  do  not  differ  so  greatly  in  shape,  the 
post-basal  swelling  for  the  accommodation  of  the  enlarged  branchial  marsu- 
pium  giving  more  uniformity  to  the  shell,  the  variation  being  principally 
in  the  width  o  f  the  shell,  which  in  old  specimens  is  very  pronounced.  Male 
shells  greatly  predominate  in  the  collections.  In  color  there  is  every 
gradation  between  a  bright  yellow  shell  with  distinct,  narrow  dark  green 
rays,  to  a  shell  that  is  dark  yellowish  or  brownish  without  rays  or  with  the 
rays  only  faintly  developed.  A  few  specimens  are  dark  brown  or  even 
pinkish  with  narrow,  greenish  rays.  Young  shells  are  very  brightly  rayed, 
the  rays  being  dark  grass-green  on  a  light  yellowish  background,  forming  a 
beautiful  surface  ornamentation.  The  rays  on  the  adult  shells  may  be 
narrow  or  broad,  or  the  broad  rays  may  be  made  up  of  many  fine  rays, 
which  may  also  be  a  trifle  wavy.  The  nacre  in  all  specimens  examined  from 
the  two  rivers  here  considered  is  pearly  white,  unmarked  by  color  of  any 
kind.  The  largest  specimens  seen  occur  at  Homer  Park;  measurements  of 
these  are  given  below: 

Length,  110;  height,  59;  breadth,  35  mm.  Male 

"       116        "68  "40  mm.  Male 

"      116        "      69  "      46  mm.  Female 

"      100        "      65  "      48  mm.  Female 

Pearly  growths  were  observed  in  many  of  the  specimens  collected. 
Occasionally  a  few  pin-head  pearls  occur  in  a  valve  but  the  greatest  number 


151]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  53 

of  abnormalities  consist  of  cyst-like  pearly  growths  near  the  posterior 
end,  in  or  near  the  adductor  muscle  and  pallial  line.  These  may  occur 
in  one  or  both  valves.  Occasionally  the  anterior  adductor  scar  is  almost 
wholly  changed  in  character  by  these  abnormal  growths.  In  several  shells 
the  space  between  the  pallial  line  and  the  margin  of  the  valve  is  stained 
purple  or  brown,  accompanied  by  few  or  many  blisters  of  various  sized. 
The  posterior  end  of  the  shell  may  also  be  afifected  so  that  it  ceases  to  grow, 
forming  a  blunt  posterior  end  marked  by  blisters  and  discolorations. 
Whether  this  condition  is  due  to  distomid  infection  as  mentioned  by 
Wilson  and  Clark  (1912  63)  as  occurring  in  Actinonaias  ligamentina  from 
the  Maumee  River  is  not  known  definitely,  but  the  inference  is  strong  that 
it  is.  It  is  noteworthy  that  the  largest  number  of  individuals  afifected  by 
parasitism  or  other  injurious  agencies  occurred  in  the  upper  part  of  the 
Salt  Fork  above  Homer  Park  dam.  Specimens  collected  from  stations 
below  the  dam,  including  Middle  Fork,  were  as  a  whole  remarkably  free 
from  pearly  growths  or  discolorations.  Occasional  individuals  from  Maho- 
met, on  the  Sangamon  River,  have  round,  pin-head  pearls  in  the  shell. 
.  Though  no  distomids  were  observed  in  the  animals  of  luteola  it  is  quite 
probable  that  these  pearls  and  blisters,  which  were  observed  for  the  most 
part  in  empty  shiells,  were  caused  by  distomid  larvae,  possibly  the  mar- 
ginal cyst  described  by  Wilson  and  Clark  (1912:62).  Many  young  shells 
of  luteola  were  collected  and  many  more  observed,  indicating  that  the 
species  is  breeding  freely  from  the  Homer  Park  section  of  the  stream  down- 
ward. No  young  shells  were  seen  above  the  Homer  Park  dam.  Gravid 
females  were  observed  at  several  places  in  September  and  October. 

A  specimen  collected  at  Mahomet  (Z11223  A)  somewhat  resembles 
Actinonaias  ligamentina  in  the  form  of  the  shell,  absence  of  strong  umbonal 
markings  and  heavy  hinge  teeth;  it  seems  to  be  one  of  those  individuals 
which  has  led  many  students  to  say  that  "ligamentina  runs  into  luteola.^' 
The  shell  is  free  of  all  abnormalities  and  has  a  clear  pearly-white  nacre. 
It  measures,  length  87,  height  54,  breadth  30  mm. 
33.  LampsUis  ventricosa  (Barnes).    Pocket-Book. 

This  large  fine  species  was  not  collected  in  Salt  Fork  above  the  station 
about  two  miles  north  of  Sidney,  16  miles  below  Urbana.  As  it  does  not 
occur  in  Spoon  River  (as  far  as  known  from  our  collections)  it  is  probably 
a  species  that  does  not  inhabit  the  smaller  tributary  streams.  From  the 
station  mentioned  as  far  down  stream  as  the  river  has  been  examined, 
including  Middle  Fork,  ventricosa  is  common  or  abundant  in  most  places. 
Below  Homer  Park  dam  it  is  abundant  and  of  large  size,  and  more  or  less 
ponderous.  The  largest  female  shell  was  found  at  Homer  Park  and  the 
largest  male  shell  in  Salt  Fork  near  Middle  Fork.  These  shells  measure  as 
follows : 

Length,  138;  height,  60;  breadth.    56  mm.    Male 
"      117        "      60  "         60  mm.     Female 


54  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [152 

Shells  from  the  Sangamon  River  are  equally  large. 

The  shape  of  the  shell  is  fairly  constant  and  there  is  little  variation 
except  in  the  females,  which  are  rounder  posteriorly  and  have  a  large  post- 
basal  swelling  for  the  enlarged  marsupia.  In  color  the  Big  Vermilion  shells 
are  all  yellowish  with  dark  green  rays  on  the  posterior  slope.  No  specimen 
was  seen  in  this  river  that  was  rayed  all  over.  Very  old  specimens  are 
entirely  rayless.  At  Mahomet,  on  the  Sangamon  River,  the  yellow  shell 
occurs  and  also  another  form  in  which  the  shell  is  yellowish-green  with 
bright,  grass-green  rays,  often  of  considerable  width.  One  specimen  is 
in  outline  like  AcHnonaias  ligamentina  and  the  surface  is  densely  covered 
with  dark  green  rays.  Two  other  specimens  have  green  rays  on  a  pink 
background,  have  pink  hinge  teeth,  and  the  whole  interior  of  the  shell  is 
pinkish.    These  bright  colored  shells  are  the  form  called  occidens  by  Lea. 

These  pink  shells  and  the  specimens  with  the  numerous  green  rays  are 
so  strikingly  different  from  the  ventricosa  as  found  in  the  Big  Vermilion 
and  also  from  the  other  shells  found  in  the  Sangamon,  that  the  name 
occidens  might  be  retained  for  these  shells  for  ecological  purposes.  The 
color  is  not  an  age  stage,  for  young  yellow  ventricosa  were  found  associated 
with  these  distinctly  rayed  forms,  and  the  rayed  forms  were  collected 
at  Mahomet  and  were  not  found  at  White  Heath  in  the  Sangamon.  The 
river  below  Mahomet  has  not  been  carefully  searched,  however,  and  the 
occidens  form  may  occur  in  some  of  this  unexplored  territory.  It  is  also 
to  be  noted  that,  as  far  as  the  material  from  these  two  rivers  is  concerned, 
the  beak  sculpture  of  the  occidens  type  of  shell  is  very  much  larger  and 
coarser  than  in  the  ventricosa  type  (Z11222).  This  form  falls  under  the 
group  of  individuals  called  mutations  by  DeVries  and  others. 

Ortmann  (1918:583)  makes  ventricosa  a  variety  or  race  of  ovata  (Say). 
As  far  as  the  authors'  experience  goes,  this  seems  unwarranted,  the  two 
species  being  as  easily  separable  as  many  other  closely  allied  species. 
Individual  specimens  from  Illinois  localities  approach  ovata  in  that  the 
posterior  ridge  is  somewhat  accentuated,  but  no  specimens  have  been  seen 
that  could  not  be  placed  readily  in  one  species  or  the  other.  Ovata  is 
reported  from  the  Ohio  River  in  Illinois  by  Marsh  but  this  species  is  more 
southern  in  its  distribution,  reaching  its  maximum  development  in  Ala- 
bama and  Tennessee.  Ventricosa  is  a  more  northern  species  attaining  its 
maximum  development  in  the  rivers  of  Illinois  and  Indiana. 

Ventricosa  is  subject  to  the  attack  of  distomid  worms  as  well  as  to 
parasitism  by  mites  (Unionicola)  and  the  material  of  this  species  from  the 
Big  Vermilion  have  suffered  more  or  less  from  this  cause.  Blisters,  pin- 
head  pearls  and  various  abnormalities  occur  in  many  individuals.  Among 
the  shells  collected  at  the  station  one  mile  above  iron  bridge  north  of  Sid- 
ney there  are  several  individuals  of  this  sort.  One  has  a  large  blister  ex- 
tending nearly  the  whole  length  of  the  ventral  margin  and  covering  the 


153]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  55 

space  between  the  margin  and  the  pallial  line.  This  was  evidently  formed 
by  distomid  parasites  (Z11058  A).  Another  specimei  from  the  same 
lot  (Z11058  B)  has  a  large  group  of  pearls  (over  100)  filling  the  space 
between  the  ventral  margin  and  the  pallial  line  over  an  area  of  about  two 
inches.  Other  specimens  have  an  abnormally  thickened  ventral  margin 
in  addition  to  blisters,  indicating  the  presence  of  some  irritating  material 
between  the  shell  and  the  mantle  lobes,  probably  mud  or  sand  (Z11149 
A).  A  specimen  from  Mahomet  had  suffered  a  curious  injury  which  had 
caused  a  large  blister  extending  from  the  upper  third  of  the  posterior  end 
to  the  center  of  the  ventral  margin,  a  distance  of  about  three  inches.  This 
was  plainly  due  to  the  presence  of  a  quantity  of  mud  getting  in  between 
the  shell  and  the  mantle,  a  small  amount  of  this  material  being  retained 
under  the  cylindrical  blister  on  the  ventral  margin.  The  outside  of  the 
shell  was  so  perfectly  repaired  that  there  was  no  evidence  of  the  pathologi- 
cal condition  within  the  shell  (Z11202  A).  Fig.  35.  This  injury  was  only 
in  the  left  valve,  the  right  valve  being  normal. 

Nearly  all  of  these  pearly  growths,  blisters,  and  abnormalities  have 
been  noted  to  occur  almost  universally  without  the  pallial  line,  between 
this  muscle  attachment  and  the  ventral,  anterior,  and  posterior  margins 
of  the  shell.  This  limited  area  is  easily  understood  when  it  is  remembered 
that  the  adductor  muscles  and  the  pallial  line  form  a  barrier  to  the  entrance 
of  foreign  material  because  the  muscles  at  these  points  are  firmly  attached 
to  the  shell  and  parasites  or  foreign  material  cannot  readily  gain  entrance 
to  the  interior  of  the  animal  between  the  mantle  and  the  shell.  This  is 
true  of  all  the  shells  of  other  species  examined  from  these  two  river  systems. 
It  was  noted  that  pearly  growths  and  abnormalities  were  rarer  in  the 
shells  from  the  Middle  Fork  and  from  Salt  Fork  near  the  Middle  Fork 
than  from  Homer  Park  and  up  the  stream  from  this  habitat.  The  shells 
from  the  Sangamon  River  at  Mahomet  were  much  less  subject  to  parasitism 
or  abnormalities  than  those  from  the  Big  Vermilion  River. 

Young  shells  of  ventricosa  were  common  only  in  Middle  Fork,  in  Salt 
Fork  near  Middle  Fork,  and  in  the  Sangamon  River  at  Mahomet.  No 
young  shells  were  collected  from  the  stream  above  the  dam  at  Homer  Park. 

Gravid  females  were  observed  on  September  26  in  the  Salt  Fork  near 
Middle  Fork  in  the  act  of  spawning.  The  shells  were  buried  in  the  sand, 
only  the  tips  of  the  siphons  showing  above  the  general  level  of  the  bottom 
of  the  stream.  The  bright  yellow  siphon  fringes,  which  are  enlarged  during 
the  spawning  period,  were  observed  to  wave  about  with  graceful  undula- 
tory  motion.  The  movements  were  more  or  less  intermittent,  a  waving 
period  being  followed  by  a  resting  stage.  These  mussels  had  well  formed 
glochidia  and  were  evidently  discharging  the  embryos  from  the  marsupia. 
These  glochidia  are  of  the  bookless  type  and  develop  in  the  mouth  of  fish 
and  the  undulatory  motions  possibly  attract  these  fish  which  may  be  thus 


56  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [154 

more  easily  infected  with  the  glochidia,  as  suggested  by  Wilson  and  Clark 
(1912:13,  14).  This  undulatory  motion  of  the  siphon  fringes  is  so  striking 
that  it  at  once  attracts  the  attention  of  an  observer,even  if  this  person  is 
not  interested  in  the  study  of  these  creatures.  Its  habit  of  burying  itself 
so  deeply  in  the  mud  or  sand  of  the  bottom  (four  to  seven  inches)  renders 
this  species  difficult  to  collect,  especially  if  the  sand  be  packed  rather  hard 
and  the  water  is  eighteen  or  more  inches  in  depth,  as  frequently  occurs. 
This  condition  was  found  in  several  of  the  Salt  Fork  habitats.  Gravid 
females  were  also  collected  from  other  localities  in  October. 

34.  LampsUis  multiradlata  (Lea). 

This  handsome  mussel  occurs  rarely  at  but  three  stations.  Homer  Park, 
near  Muncie,  and  in  Middle  Fork.  It  is  common  in  the  Big  Vermilion 
below  Middle  Fork.  The  specimens  from  the  Salt  Fork  Stations  are  all 
small  for  the  species,  being  not  over  half  the  size  of  individuals  from 
White  River,  near  Muncie,  Indiana,  and  the  hinge  teeth  are  much  weaker 
than  those  from  Indiana  streams.  This  is  especially  true  of  the  pseudo- 
cardinal  teeth  which  are  narrower  and  more  elongated  than  the  speci- 
mens examined  from  other  streams.  Individuals  from  Homer  Park 
are  brilliantly  rayed,  grass  green  on  a  yellowish  ground.  Middle  Fork 
specimens  are  not  as  brilliantly  rayed,  the  general  color  being  yellowish 
with  scanty  rays.  The  largest  specimens  collected  measure  as  follows, 
a  specimen  from  Muncie,  Indiana  also  being  included  for  comparison: 

Length,  34;  height,  22  mm.  Homer  Park. 

"      43        "      31mm.  Middle  Fork.    Male 

"      69        "      55  mm.  Big  Vermilion.    Female 

"85        "64  mm.  Muncie,  Ind.    Female 

This  species  is  rare  in  Illinois  waters,  judging  by  the  few  records 
available.  These  indicate,  however,  a  wide  range  over  the  State,  from 
Cook  County  to  southern  Illinois  (Baker,  1906:64).  Ortmann  (1918:584, 
1920:309)  adopts  the  nzme  fasciola  of  Rafinesque  (1820)  for  this  species, 
stating  that  the  original  description  of  Rafinesque  is  definite  enough  to 
indicate  without  much  question  a  shell  of  the  multiradiata  type.  If 
this  be  so,  then  Lea's  very  appropriate  name  must  give  place  to  the 
one  used  at  an  earlier  date  by  Rafinesque.  The  species  has  not  been 
recorded  from  the  Sangamon  River. 

35.  LampsUis  anodontoides  (Lea).    Yellow  Sand  Shell. 

This  fine  shell,  which  is  usually  abundant  throughout  Illinois  waters, 
was  collected  at  only  three  stations  in  the  Big  Vermilion  River,  all  of 
which  were  below  the  dam  at  Homer  Park.  The  largest  and  finest  in- 
dividuals occur  at  Homer  Park  and  the  smallest  were  collected  in 
Middle  Fork.      Specimens  from  the  first  named    station  have  a  yel- 


155J  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  57 

lowish  shell  with  little  or  no  indication  of  rays.  Middle  Fork  specimens 
include  yellowish  shells  without  rays,  as  well  as,  more  rarely,  individ- 
uals with  rather  bright,  wide  rays,  approaching  in  this  respect  the 
related  species  fallaciosa  of  Simpson.  The  largest  specimens  from  the 
two  localities  measure  as  follows: 

Length,  124;  height  57;  breadth  47  mm.    Male,  Homer  Park. 

90        "      41  "     33  mm.    Female,  Middle  Fork. 

The  nacre  is  tinted  with  pinkish  or  salmon  color.  Pearly  growths 
are  not  uncommon  in  specimens  from  the  Big  Vermilion.  These  are 
in  the  form  of  blisters  and  pin-head  pearls,  which  are  usually  confined 
to  the  margin  of  the  shell  between  the  pallial  line  and  the  external  margin 
of  the  valve.  One  individual  from  Homer  Park  had  the  entire  area  between 
the  pallial  line  and  the  ventral  margin  of  the  shell  abnormally  enlarged 
and  thickened,  due  possibly  to  the  presence  of  distomid  larvae  and  to  some 
extent  to  the  intrusion  of  small  amounts  of  soil  between  the  mantle  and 
the  animal  (Z11147A).  Specimens  from  Middle  Fork  are,  as  a  rule, 
free  from  pearls  and  abnormal  growths.  Gravid  females  were  found  on 
September  26  in  Middle  Fork,  and  on  July  30  in  Salt  Fork  at  Homer 
Park.  Anodontoides  has  not  been  recorded  from  the  Sangamon  River  at 
Mahomet  or  in  the  other  places  examined. 

The  early  writers,  Say,  Conrad,  and  others,  have  identified  this  species 
with  the  EUiptio  teres  of  Rafinesque  (1820)  and  if  the  shell  is  clearly  identi- 
fiable from  the  description  of  Rafinesque  the  familiar  name  of  Lea  must 
become  a  synonym. 

36.  Truncilla  (Pilea)  perplexa  rangiana  (Lea). 

Four  specimens  of  this  race  of  perplexa  are  in  the  naiad  collection 
of  the  Museum  of  Natural  History,  University  of  Illinois,  collected 
by  Mr.  A.  A.  Hinkley,  in  the  Big  Vermilion  River  at  Danville.  Three 
are  females  and  one  is  a  male.  They  are  much  smaller  than  specimens 
from  Florence,  Alabama,  where  the  species  attains  its  greatest  develop- 
ment. The  male  and  largest  female  shell  measure  as  follows,  corre- 
sponding measurements  being  also  given  for  the  Alabama  shells. 

Length,  41;  height,  29;  breadth,  22  mm.  Danville,  male,  Z3770. 

"      44  '      "      34  "       20  mm.  Danville,  female,  Z3770, 

"      55        "      43  "      32  mm.  Alabama  male,  Z3947. 

'•      73        "      53  "      35  mm.  Alabama  female,  2^947. 

As  no  specimens  of  Truncilla  were  found  in  the  Big  Vermilion  or  its 
tributaries  as  far  down  as  Middle  Fork,  which  is  but  a  few  miles  west 
of  Danville,  this  species  evidently  does  not  inhabit  the  stream  above  the 
locality  from  which  Hinkley  collected  his  shells.  Truncilla  perplexa 
as  well  as  its  variety  rangiana  is  known  in  Illinois  only  from  the  Ohio 


58  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [156 

and  Wabash  rivers.  The  small  size  of  the  Danville  specimens  may  be 
due  to  the  fact  of  their  inhabiting  the  upper  part  of  their  distributional 
range,  in  a  rather  small  river.  Rafinesque's  name  torulosa  has  been 
used  by  Conrad,  Agassiz,  Reeve,  and  Ortmann  for  Truncilla  perplexa 
and  if  the  original  description  is  clear  enough  to  reasonably  fix  the  shell 
as  Lea's  perplexa  this  form  will  stand  as  Truncilla  torulosa  rangiana 
(Lea).  Neither  perplexa  or  rangiana  are  known  from  the  Sangamon  River. 

FAMILY  SPHAERIIDAE 

37.  Sphaerium  striatinum  (Lamarck).    Variety. 

This  finger-nail  clam  occurs  abundantly  only  in  the  ditch  north  of 
Urbana.  It  also  occurred  infrequently  in  Spoon  River,  and  near  the 
iron  bridge  in  Salt  Fork  north  of  Sidney.  Dead  specimens  were 
found  at  bench  mark  655  and  below  the  Homer  Park  dam. 

Sterki  remarks  of  this  form  "possibly  a  form  of  striatinum  Lam; 
apparently  the  same  as  a  Sphaerium  from  Iowa  and  other  places  which  for 
many  years  has  been  left  unnamed,  except  in  manuscript.  It  still  seems 
impossible  to  say  where  the  limits  of  striatinum  are."  The  writer  fully 
agrees  with  Dr.  Sterki  regarding  the  variation  in  this  common  species. 
This  variety  appears  quite  distinct  from  the  ordinary  specimens  of  the 
species  and  it  is  to  be  hoped  that  Dr.  Sterki  wUl  give  it  a  name.  It  is 
noteworthy  that  the  form  occurs  commonly  only  in  the  drainage  ditch  above 
Urbana  and  was  not  found  in  any  numbers  below  this  place.  A  Sphaerium 
identified  as  striatinum  by  Zetek  some  years  ago,  occurring  in  Crystal  Lake, 
was  doubtless  this  form. 

38.  Sphaerium  stamineum  (Conrad). 

This  small  mussel  is  abundant  at  several  places  in  Salt  Fork  above 
Sidney.  It  occurs  only  infrequently  at  two  other  places.  Reported  by 
Zetek  from  Crystal  Lake.  Some  of  the  shells  are  typical  but  others  are 
similar  to  straitinum  and  it  is  difi6cult  to  separate  some  specimens  from  that 
species.  At  the  station  called  bench  mark  655  a  form  of  this  species 
occurs  that  is  somewhat  like  the  variety  forbesi  Baker,  described  from 
Mason  County,  Illinois. 

39.  Sphaerium  solidulum  (Prime). 

An  abundant  species  in  the  Spoon  River  and  in  the  Salt  Fork  above 
Sidney.  Occurs  rarely  at  other  places.  Reported  by  Zetek  from  Crystal 
Lake.    On  the  whole  this  species  is  quite  uniform  in  characters. 

40.  Sphaerium  species. 

A  Sphaerium  occurs  abundantly  in  Salt  Fork  below  the  Homer  Park 
dam  which  is  thought  by  Sterki  to  be  possibly  a  new  species.  It  is  related  to 
solidulum  but  is  larger  and  more  robust  (mus.  no.  Z11383).     It  lives  in 


157]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  59 

shallow  water  on  a  more  or  less  rocky  bottom  a  short  distance  below 
the  dam. 

41.  Musculium  transversum  (Say). 

This  fragile  finger-nail  clam  is  apparently  rare  in  Salt  Fork  and  its 
tributaries,  occurring  only  in  Salt  Fork  near  Sidney.  It  has  been  reported 
from  Crystal  Lake  by  Zetek.    The  specimens  are  typical. 

42.  Musculium  truncatum  Linsley. 

This  very  small  clam  was  found  only  in  the  old  river  bed  near  the 
cemetery  north  of  Urbana.    Here  it  is  common  and  typical. 

43.  Musculium  partumeium  (Say). 

Reported  by  Zetek  from  Crystal  Lake.    It  has  not  been  found  recently. 

44.  Pisidium  compressum  Prime. 

This  small  clam  occurs  in  abundance  only  at  the  iron  bridge  north  of 
Sidney.  A  few  specimens  were  found  below  the  natural  dam  in  Salt  Fork. 
The  individuals  are  quite  typical. 

45.  Pisidium  kirklandi  Sterki. 

A  single  specimen  of  this  species  was  foumd  at  the  iron  bridge  north 
of  Sidney.    It  is  apparently  very  rare. 

46.  Pisidium  splendidulum  Sterki. 

A  few  specimens  of  this  tiny  species  were  found  in  the  Salt  Fork  near 
Muncie.    The  individuals  are  young  and  not  quite  typical. 

The  distribution  of  the  Sphaeriidae  in  Salt  Fork  is  interesting  and 
significant  in  connection  with  the  sewage  pollution  of  the  stream.  It 
will  be  noted  that  no  Sphaeriidae  were  found  in  the  Salt  Fork  between  the 
Urbana  ditch  and  the  station  called  natural  dam,  14  miles  below  Urbana. 
These  mussels  are  characteristic  mud  dwellers  and  their  absence  from  the 
intervening  territory  in  the  stream  is  striking  evidence  of  the  unfavorable 
conditions  on  the  bottom.  They  were  not  found  in  abundance  above 
bench  mark  655.  It  will  also  be  noted  that  Sphaerium  appears,  living, 
before  Pisidium  and  is  also  found  in  abundance  higher  up  the  stream. 
This  may  mean  that  Sphaerium  is  better  able  to  withstand  these  adverse 
conditions  than  Pisidium,  which  is  more  of  a  mud  dweller.  Pisidium  is 
much  less  common  everywhere  in  the  stream  and  but  one  species  occurs 
abundantly  at  one  place  (Table  IV). 

FAMILY  PLEUROCERIDAE 

47.  Pleurocera  elevatum  (Say). 

This  long-spired  snail  is  rare  or  wanting  in  most  parts  of  the  Big 
Vermilion  River.  Two  white,  weathered  specimens  of  this  species  were 
found  below  the  natural  dam  in  Salt  Fork.    They  may  have  been  washed 


60  JLUNOIS  BIOLOGICAL  MONOGRAPHS  [158 

from  a  post-glacial  fossil  deposit.  None  were  found  either  alive  or  dead 
in  any  other  part  of  the  Big  Vermilion  examined,  excepting  the  two  speci- 
mens mentioned  above. 

In  the  Sangamon  River,  at  Mahomet,  elevatum  is  very  abundant  on  a 
sandy  bottom  in  water  a  foot  in  depth  (low  water  period).  The  speci- 
mens are  large  (maximum  length  35  mm.)  and  vary  in  color  from  light  yel- 
lowish to  black  or  dark  chestnut  with  a  light  zone  below  the  suture.  The 
characteristic  peripheral  keel  is  developed  on  the  majority  of  specimens 
and  ascends  the  spire  just  above  the  suture.  In  a  few  individuals  this  keel 
is  absent  and  the  body  whorl  is  rounded.  Many  intermediate  forms  occur 
connecting  these  rounded  shells  with  the  more  distinctly  keeled  forms. 
Usually  there  are  from  one  to  six  spiral  ridges  on  the  base  of  the  shell  extend- 
ing longitudinally  parallel  with  the  peripheral  keel.  The  strongly  carinate 
whorls  of  the  young  shell  are  six  in  number  and  these  lose  their  sharpness 
more  or  less  abruptly  on  the  seventh  whorl.  No  individuals  were  seen  in 
which  the  protoconch  or  nucleus  of  the  first  whorl  was  preserved.  Young 
and  half-grown  specimens  have  two  brown  bands  on  the  spire  whorls  and 
four  bands  on  the  body  whorl  and  base  of  the  shell.  This  species  also  occurs 
in  the  Sangamon  at  White  Heath,  and  it  has  been  found  in  several  Pleisto- 
cene deposits  near  Mahomet,  the  white  shells  of  the  fossils  being  washed 
out  of  the  bank  by  periods  of  high  water. 

48.  Goniobasis  livescens  Menke. 

This  river  snail  occurred  in  but  four  places  in  Salt  Fork.  It  was 
infrequent  at  bench  mark  655  and  abundant  just  below  the  dam  at  Homer 
Park  and  near  Muncie.  It  is  abundant  in  the  big  Vermilion  below  Middle 
Fork.  It  has  been  identified  by  local  naturalists  as  Goniobasis  pulchella 
Anthony  and  has  been  reported  as  this  species  by  other  students  as  from  the 
Big  Vermilion  River  (Baker,  1906:98).  Specimens  were  sent  to  Mr.  Calvin 
Goodrich,  who  is  making  a  study  of  this  family,  and  were  identified  as 
livescens.  I  quite  agree  with  Mr.  Goodrich  that  they  are  livescens  rather 
than  pulchella.  Young  and  immature  specimens  are  banded  ViiktGoniobasis 
depygis  Say. 

Goniobasis  semicarinata  Say  is  reported  from  the  Big  Vermilion  River 
by  Marsh  (B3,ker,  1906:98)  but  no  specimens  have  been  seen  from  this 
stream.  The  species  may  live  in  the  river  below  Danville  or  the  citation 
may  be  based  on  long-spired  livescens. 

FAMILY  AMNICOLIDAE 

49.  Pomatiopsis  lapidaria  (Say). 

This  tiny  snail  is  abundant  in  small,  cold  streams  flowing  into  the 
Sangamon  River.  At  one  locality,  about  three-fourths  of  a  mile  below 
Mahomet,  it  was  extremely  abundant  in  a  small  brook  about  two  feet 


159]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  61 

wide  and  not  exceeding  six  inches  in  depth.  The  bottom  was  of  mud  and 
fine  sand.  The  largest  specimen  measures  7  mm.  in  length.  This  spe- 
cies was  not  collected  from  streams  flowing  into  the  Big  Vermilion  River. 

50.  Amnicola  limosa  (Say). 

This  common  Amnicola  occurred  at  three  stations,  only  two  of  these 
yielding  living  specimens.  At  the  station  above  the  iron  bridge  north  of 
Sidney,  the  shells  were  secured  by  sweeping  the  vegetation  bordering  the 
shore  with  the  Walker  dredge.  The  limosa  from  the  Salt  Fork  are  rather 
corpulent  but  are  not  as  globular  as  the  variety  known  as  porata  (Say).  It 
is  noteworthy  that  this  species  (and  in  fact  the  genus)  should  be  found  only 
in  a  stretch  of  the  stream  three  miles  in  length,  from  16  to  19  miles  below 
Urbana.  None  were  seen  below  the  dam.  Individuals  were  rare  and 
difficult  to  find.  Near  the  cement  bridge  east  of  Sidney,  dead  shells 
occurred  among  water  plants  {Nymphaea  advena)  but  no  living  specimens 
could  be  found.  Limosa  was  not  collected  at  the  stations  in  the  San- 
gamon River. 

51.  Amnicola  (Cincinnatia)  cincinnatiensis  (Anthony). 

This  Amnicola  occurred  rarely,  but  living,  at  but  two  stations  in  the 
Salt  Fork,  16  and  17  miles  below  Urbana.  The  largest  and  only  adult 
individual  collected  measures  6  mm.  in  length.  Several  half-grown  shells 
were  found.  About  two  years  ago  Mr.  James  Zetek  found  cincinnatiensis 
near  St.  Joseph.  A  careful  search  of  this  region,  both  in  the  Salt  Fork 
and  in  the  small  streams  flowing  into  Salt  Fork,  failed  to  produce  a  single 
specimen  of  this  species.  During  the  intervening  ten  years  the  species 
appears  to  have  died  out,  either  from  the  effect  of  sewage  pollution  or 
from  some  other  unknown  cause. 

FAMILY  VIVIPARIDAE 

52.  Campeloma  rufum  (Haldeman). 

The  Campelomas  of  the  Big  Vermilion  all  appear  to  be  referable  to 
Haldeman's  rufum.  The  shell  is  more  or  less  pinkish,  especially  on 
the  spire.  One  specimen  from  the  iron  bridge  north  of  Sidney  resembles 
Haldeman's  figure  1  on  plate  3  of  the  Monograph,  which  is  the  type 
of  rufum.  Specimens  from  Homer  Park,  below  the  dam,  are  strongly 
suggestive  of  integrum  (Say),  many  of  the  individual  shells  being  like 
Binney's  figure  96  which  represents  Say's  integrum.  With  these  are 
short-spired  shells  recalling  the  obesum  of  Lewis  as  figured  by  Binney 
(figure  95).  These  are  not  quite  like  the  figures  of  Lewis  (1875,  pi.  23, 
figs.  4-5)  which  are  rather  broader.  Variation  in  rufum  seems  to  parallel 
that  of  integrum  in  the  length  of  the  spire.  Typical  integrum  has  a  white 
aperture  and  a  bright  green  shell  devoid  of  the  peculiar  pink  tint  of  rufum. 


62  ,     ILUNOIS  BIOLOGICAL  MONOGRAPHS  [160 

The  rujum  from  Homer  Park  have  the  spire  whorls  more  or  less  gibbous, 
strongly  shouldered,  the  first  three  whorls  seeming  to  be  telescoped  into 
the  later  whorls.  In  this  respect  they  resemble  integrum  obesum  as  sug- 
gested above.  Measurements  of  a  few  of  the  Homer  Park  specimens  are 
given  below  (Zl  1168): 

Length,  37;  breadth,  24;  aperture  length,  21;  breadth,  14  mm. 
"      33  "      22  "  "      19  "      13  mm. 

"      30  "      21  "  "      18  "      12  mm. 

To  this  and  other  lots  of  Campelomae  from  the  Big  Vermilion  River  the 
statement  of  Lewis  may  be  well  applied:  "These  and  many  other  forms  in 
my  collection,  all  part  of  a  series,  go  far  to  show  that  it  is  unsafe  to  attempt 
to  decide  the  limits  of  species  from  a  few  individuals"  (1875:337). 

The  distribution  of  this  species  in  Salt  Fork  is  interesting  and  sug- 
gestive. Living  specimens,  small  and  few  in  number,  were  found  over  two 
miles  upstream  in  Spoon  River.  Dead,  mostly  old  and  bleached  shells, 
were  collected  at  nearly  all  stations  in  the  Salt  Fork,  but  living  shells  of 
rufum  were  not  seen  above  the  station  two  miles  north  of  Sidney.  Here 
only  one  living  specimen  could  be  found.  A  mile  farther  down  the  stream 
another  living  specimen  was  collected.  The  presence  of  so  many  dead 
shells  with  so  few  living  individuals  above  the  Homer  Park  dam  indicates 
clearly  an  unfavorable  environment.  There  are  many  normal  and  favor- 
able habitats  for  this  mollusk  in  this  stretch  of  nearly  twenty  miles  in  Salt 
Fork  and  the  unfavorable  agencies  must  be  wholly  those  contributed  by 
Man — the  disposal  of  sewage  and  other  wastes  by  means  of  this  stream. 
Below  Homer  Park  dam  the  species  is  abundant  and  as  fine  as  can  be 
found  anywhere.  Rufum  is  rare  on  a  sand  and  gravel  bottom  and  abundant 
on  a  mud  bottom. 

The  Campelomae  from  the  Sangamon  River  at  Mahomet  are  also  refer- 
able to  rufum.  The  spire  is  longer  and  the  shell  narrower,  however,  than  in 
the  Salt  Fork  specimens,  and  there  is  no  tendency  to  vary  toward  the 
obesum  form  of  shell.  The  interior  of  the  aperture  is  slightly  pinkish.  One 
specimen  from  Mahomet  has  a  very  heavy  shell  recalling  the  subsolidum 
of  Anthony,  a  common  species  in  most  parts  of  Illinois  but  absent  from 
either  of  the  rivers  under  consideration.  Reversed  individuals  are  rare, 
only  one  specimen  being  found  in  the  Sangamon  River,  a  mile  below 
Mahomet.    This  is  a  young  individual. 

The  air-breathing  snails,  belonging  to  the  genera  Physa,  Ferrissia, 
Planorbis,  and  Galba,  are  better  able  to  withstand  the  ill  effects  of  sew- 
age and  other  stream  pollution  than  are  their  relatives,  the  snails  and 
clams  that  take  their  oxygen  directly  from  the  water  (dissolved  oxygen). 
They  were  therefore  found  in  Salt  Fork  in  places  where  the  water  breathers 
were  entirely  wanting,  as  at  St.  Joseph  and  the  first  stations  below.   It  has 


161]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  63 

been  observed  in  other  places,  notably  in  the  Genesee  River,  at  Rochester, 
N.  Y.,  where  sewage  pollution  was  at  one  time  very  severe,  that  these 
pulmonate  water  snails  were  the  last  to  succumb  to  the  toxic  influences 
of  pollution  and  they  have  been  known  to  live  in  water  that  was  filled 
with  putrescent  matter  and  also  in  water  strongly  impregnated  with  arsenic. 
When  these  snails  begin  to  disappear,  conditions  must  indeed  be  deplorable. 

FAMILY  ANCYLIDAE 

53.  Ferrissia  rivularis  (Say).    River  Limpet. 

The  tiny  limpet-like  shell  known  as  Ancylus  (Ferrissia)  rivularis  was 
very  abundant  in  parts  of  Salt  Fork,  its  usual  habitat  being  the  inside  of 
empty  valves  of  the  naiades.  The  individuals  are  large  (6.4  mm,  in  length) 
and  fine  and  apparently  normal  in  form.  This  species  was  found  alive  at 
St.  Joseph  where  pollutional  conditions  are  bad,  and  was  also  abundant 
at  the  stations  lower  down  the  stream  where  living  mussels  or  pectinibran- 
chiate  snails  were  very  rare  or  absent.  Ancyli  were  not  observed  in  Spoon 
River,  in  Middle  Fork,  or  below  the  dam  at  Homer  Park.  Found  by  Mr. 
Zetek  in  the  Sangamon  River  at  White  Heath. 

54.  Ferrissia  tardus  Say.    River  Limpet. 

This  Ancylus  is  in  the  author's  collection  from  White  Heath  and 
Monticello,  Sangamon  River,  and  from  the  Salt  Fork  near  Urbana,  col- 
lected by  Mr.  Zetek  and  identified  by  Dr.  Bryant  Walker.  No  tardus 
were  collected  during  the  present  survey. 

55.  Gundlachia  meekiana  Stimpson. 

Specimens  of  this  characteristic  mollusk  are  in  the  author's  collection 
from  Crystal  Lake,  Urbana,  collected  by  Mr.  Zetek  in  August  1904,  and 
identified  by  Dr.  Walker.   None  were  seen  during  the  present  survey. 

In  the  catalogue  of  the  MoUusca  of  Illinois  (Baker,  1906:  101,  102) 
Ancylus  (Ferrissia)  skimekii  Pilsbry  is  recorded  from  Salt  Fork,  Urbana, 
and  Ancylus  (Laevapex)  kirklandi  Walker  from  Crystal  Lake,  Urbana. 
These  species  were  contained  in  the  collection  of  the  State  Laboratory 
of  Natural  History.  A  recent  examination  of  the  material  upon  which 
these  records  are  based  indicates  that  there  has  been  an  error  in  the  habitat 
given.  -  None  are  from  the  Salt  Fork  or  Crystal  Lake.  Ancylus  kirklandi, 
identified  by  Walker,  is  in  the  laboratory  collection  from  Havana,  Illinois 
River  (Nos.  13792,  13811,  24123)  and  Elizabethtown,  Illinois  (No.  24527). 
Ancylus  shimekii  (No.  24541)  is  in  a  bottle  with  Ancylus  rivularis,  both 
identified  by  Walker.  The  bottle  is  without  locality  and  no  record  was 
found  in  the  laboratory  catalogs  of  the  specimens  bearing  this  number. 
It  is  evident,  therefore,  that  these  species  of  Ancylus  must  be  eliminated 
from  the  list  of  the  fauna  of  Salt  Fork. 


64  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [162 

FAMILY  PHYSIDAE 

56.  Physa  gyrina  Say.    Tadpole  Snail. 

This  snail  is  usually  abundant  wherever  found.  In  the  old  cut-offs 
of  the  Salt  Fork  above  Urbalia,  as  well  as  in  the  ditch  north  of  Urbana, 
it  is  abundant  and  quite  typical  with  long,  slender  shell  and  spire,  the 
immature  individuals  with  a  short,  dome-shaped  spire.  Below  St.  Joseph, 
where  it  occurs  sparingly,  the  shell  is  broader  and  even  in  adult  specimens 
the  spire  is  more  or  less  dome-shaped.  Gyrina  is  more  common  above  than 
below  the  dam  at  Homer  Park.  The  species  is  more  characteristic  of  slow- 
moving,  pond-like  bodies  of  water  than  of  larger  streams.  It  occurs  also 
in  Stony  Creek  near  Muncie,  in  a  small  pond  near  Middle  Fork,  and  in 
the  Big  Vermilion  below  Middle  Fork. 

57.  Physa  crandalli  Baker. 

Specimens  of  a  Physa  with  a  shouldered  whorls,  a  wide  body  whorl, 
the  shell  thick  and  heavy  for  the  genus  are  referred  to  crandalli.  This 
mollusk  is  abundant  in  the  drainage  ditch  above  Urbana  associated  with 
gyrina.  None  were  found  in  the  cut  offs  of  the  old  stream  and  the  species 
probably  does  not  inhabit  the  pond-like  habitats  in  which  gyrina  is  usually 
found,  preferring  running  water.  The  specimens  referred  to  sayii  Tappan, 
from  Urbana  (Baker,  1906:99)  are  also  this  species.  It  is  noteworthy  that 
living  specimens  of  this  species  were  collected  at  St.  Joseph  where  polluted 
conditions  are  bad.  None  were  found  below  the  iron  bridge  one  mile 
north  of  Sidney,  or  in  any  part  of  the  Salt  Fork  below  this  point.  Charac- 
teristic specimens  were  collected  in  the  Big  Vermilion  below  Middle  Fork, 
on  a  stony  bottom  in  riffles. 

FAMILY  PLANORBIDAE 

58.  Planorbis  (Helisoma)  trivolvis  Say.    Wheel  Snail. 

This  species  of  wheel  snail  is  apparently  not  common  in  Salt  Fork,  only 
scattering  specimens  being  found  along  the  stream.  It  occurred  more 
abundantly  in  a  small  stream,  dry  in  summer,  which  runs  through  low. 
swampy  grotmd  on  the  east  bank  of  Salt  Fork  south  of  the  interurban 
bridge  at  St.  Joseph.  Living  trivolvis  were  not  found  in  the  stream  above 
the  first  bridge  below  St.  Joseph,  twelve  miles  below  Urbana.  Even  this 
air-breathing  snail  seems  to  be  unable  to  live  in  any  abundance  in  the 
polluted  water  of  South  Fork. 

59.  Planorbis  (Helisoma)  pseudotrivolvis  Baker. 

This  recently  described  wheel  snail  (Baker,  1920:123)  occurs  abun- 
dantly in  the  old  stream  bed  (cut-offs)  of  the  Salt  Fork  near  the  Woodlawn 
cemetery,  Urbana,  and  it  is  here  the  predominating  species  of  the  genus, 
true  trivolvis  being  rare.    The  differences  between  this  species  and  trivolvis 


1631  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  ^ 

have  been  clearly  pointed  out  in  the  paper  referred  to  above.  Two  speci- 
mens, one  living,  referable  to  this  species  were  found  in  Salt  Fork  about 
two  miles  below  St.  Joseph,  associated  with  typical  trivolvis. 

60.  Planorbis  (Helisoma)  antrosus  Conrad. 

A  single,  small,  bleached  shell  of  this  species  was  found  near  the  cement 
bridge  northeast  of  Sidney.  It  may  have  been  washed  from  a  Pleistocene 
fossil  deposit  near  by.    None  were  collected  living. 

61.  Planorbis  (Gyraulua)  parvus  Say. 

This  small  species  was  found  in  limited  number  associated  with  Planar^ 
bis  trivolvis  and  Galba  parva  in  the  low  ground  subject  to  spring  overflow 
south  of  the  interurban  bridge  at  St.  Joseph.  It  was  typical  in  form  as 
compared  with  authentic  specimens  collected  near  Philadelphia  by  Dr. 
H.  A.  Pilsbry.    None  were  found  in  Salt  Fork  or  in  the  Sangamon  River. 

FAMILY   LYMNAEIDAE 

62.  Galba  parva  (Lea). 

This  tiny  pond  snail  was  found  at  but  one  place  in  the  Salt  Fork.  A 
dead  shell  was  obtained  at  the  iron  bridge,  a  mile  north  of  Sidney.  In 
the  low  ground  south  of  the  interurban  bridge  at  St.  Joseph  before  referred 
to,  parva  occurs  abundantly  in  the  bed  of  a  small  stream  which  has  water 
in  it  only  in  spring  and  early  summe'r.  On  the  Sangamon  River,  this  species 
was  noted  in  abundance  on  wet  mud  flats  bordering  the  margin  of  the 
stream.  This  locality  was  about  three-fourths  of  a  mile  below  Mahomet. 
The  polluted  water  at  St.  Joseph  appears  to  have  little  effect  on  this  species 
or  the  other  pulmoniferous  mollusks  associated  with  it.  It  is  probable 
that  at  the  times  of  high  water  so  much  oxygen  is  mixed  with  the  upper 
layer  which  overflows  these  low  places  that  the  ill  effect  of  sewage  pollution, 
from  decomposition  of  organic  matter,  is  so  reduced  in  quantity  and  quality 
as  to  be  little  noticed  by  these  air-breathers. 

63.  Galba  humilis  modicella  (Say). 

This  is  usually  a  very  common  species  where  it  occurs  at  all.  It  is  rare, 
however,  in  the  Big  Vermilion,  scattered  specimens,  mostly  dead  shells, 
being  found  at  four  stations.  It  was  collected  living  in  the  drainage  ditch 
above  Urbana,  in  Crystal  Lake  (Zetek) ,  and  a  large  typical  individual  was 
found  alive  on  the  mud  bordering  the  stream  a  short  distance  below  the 
mouth  of  Spoon  River  in  Salt  Fork  west  of  St.  Joseph.  The  species  occurs 
sparingly  in  the  Sangamon  River  associated  with  Galba  parva  at  the  locality 
mentioned  under  that  species.  In  a  small  pond  in  the  gravel  pit  north  of 
the  interurban  tracks  west  of  the  Middle  Fork,  modicella  occurs  living 
among  cat-tails  {Typha)  associated  with  Physa  gyrina. 


66  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [164 

64.  Galba  obrussa  (Say). 

Obrussa  occurs  in  Stony  Creek  near  Muncie,  collected  by  Mr.  John  R. 
Malloch,  May  29,  1919.    The  specimens  are  typical  though  small. 

65.  Galba  caperata  (Say). 

This  species  occurs  abundantly  in  swampy  woodlands  bordering  the 
Salt  Fork  about  three  miles  north  of  Urbana,  the  ground  in  dry  weather 
being  almost  paved  with  the  dead  shells  of  this  snail.  Some  of  the  snails 
escape  the  dry  period  by  crawling  into  cracks  and  holes  and  there  hiber- 
nating. This  species  has  not  been  found  in  or  near  Salt  Fork  or  the  other 
tributaries  of  the  Big  Vermilion  River.  Because  of  its  preference  for  small, 
summer-dry  ponds  and  pools  this  Galba  will  not  be  found,  probably,  in  any 
part  of  the  streams  herein  considered. 


165]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  67 


POLLUTION  OF  SALT  FORK  BY  SEWAGE  AND 
MANUFACTURING  WASTES 

GENERAL  NATURE  OP  STREAM  POLLUTION 

Stream  pollution  may  be  broadly  divided  into  two  main  divisions: 
contamination  by  organic  sewage  from  cities  and  towns  and  by  chemical 
wastes  from  factories  and  mines.  Both  are  inimical  to  life  but  the  latter 
is  especially  fatal  to  animal  life,  causing  wide  stretches  of  otherwise 
fertile  streams  to  become  veritable  deserts.  Organic  sewage,  in  a  crude 
or  highly  concentrated  form,  is  also  very  injurious,  effectually  eliminating 
most  forms  of  life  from  the  polluted  body  of  water. 

The  importance  and  seriousness  of  the  problem  of  stream  pollution  in 
its  effect  on  the  life  of  the  rivers  and  streams  into  which  the  contaminating 
material  is  discharged  has  not  until  very  recently  been  given  the  attention 
the  subject  demands.  The  diminishing  fish  supply,  and  in  many  places 
the  very  objectionable  physical  character  of  the  polluted  waters,  have 
caused  the  authorities  of  several  states  to  pass  laws  governing  the  discharge 
of  these  wastes  into  streams  and  the  establishment  of  penalties  for  dis- 
regarding these  laws.  New  York  and  Massachusetts  have  led  in  the  fram- 
ing of  these  laws  and  other  states  are  following  the  good  example  set  by 
these  two  older  commonwealths,  where  the  conditions  seem  to  have  reached 
a  maximum  of  harmfulness  (see  Ward,  1918,  1919). 

During  recent  years  stream  pollution  has  enormously  increased  and  the 
problems  arising  from  this  condition  have  been  investigated  by  many 
biologists  and  sanitary  engineers.  The  former  have  studied  the  problem 
from  the  viewpoint  of  its  effect  on  the  useful  animal  life,  especially  fishes 
and  river  mussels,  and  this  phase  probably  bears  as  close  a  relation  to 
human  welfare  as  any  other.  Of  course,  from  the  standpoint  of  health,  the 
pollution  problem  is  of  paramount  importance  because  of  its  bearing  on 
such  diseases  as  typhoid  fever  which  may  be  caused  by  a  polluted  water 
supply. 

Perhaps  the  worst  effect  of  chemical  pollution  is  to  be  found  in  the 
streams  of  western  Pennsylvania,  where  water  heavily  loaded  with  oil  or 
acid  water  from  coal  mines  is  permitted  to  flow  into  the  rivers  and  streams 
of  this  part  of  the  state.  Studies  by  Ortmann  (1909)  show  that  whole 
stretches  of  the  Allegheny,  Ohio,  and  Monongahela  rivers  have  been  made 
into  deserts,  as  far  as  the  animal  life  is  concerned,  by  the  large  amount  of 
poisonous  substances  discharged  into  these  streams  by  the  mines,  oil  indus- 


68  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [166 

tries,  and  chemical  and  other  factories  that  border  these  rivers.  In  the 
Susquehanna  River  the  same  condition  prevails  in  many  places  (Leighton, 
1904).  Such  pollution  causes  a  complete  extermination  of  the  fauna 
(and  largely  of  the  flora)  and  leaves  the  streams  in  such  condition  that 
restocking  by  either  natural  or  artificial  means  is  practically  impossible. 

Pollution  by  sewage,  when  the  polluting  material  is  of  small  percentage 
as  compared  with  the  pure  water  of  the  stream  (as  200  to  1),  causes  little 
inconvenience  to  the  animal  life  and  is  doubtless  of  some  benefit  because  of 
the  additional  food  material  that  is  added  (Forbes  and  Richardson,  1919: 
146).  But  the  streams  seldom  remain  long  in  this  innoxious  condition,  the 
sewage  becoming  more  and  more  concentrated  until  the  whole  stream 
may  be  supersaturated  with  noxious  substances,  the  amount  of  oxygen  in 
saturation  reduced,  and  the  biota  finally  driven  out  or  killed. 

The  Illinois  River  is  one  of  the  most  striking  examples  of  the  effect  of 
sewage  pollution  on  the  life  of  a  stream.  Under  the  direction  of  Dr.  S.  A. 
Forbes,  studies  of  this  river  have  been  carried  on  for  more  than  forty-two 
years  (since  1877)  and  a  mass  of  reliable  data  has  been  gathered.  The  open- 
ing of  the  Chicago  Drainage  Canal  in  1890  produced  most  revolutionary 
changes  in  the  life  of  the  Illinois  river,  by  the  discharge  into  it  of  the 
sewage  of  Chicago  as  well  as  commercial  wastes  from  this  city  and  other 
places  along  the  river  (Forbes  and  Richardson,  1913,  1919).  The  effect 
of  this  sewage  pollution  has  been  to  cause  the  animal  life  to  be  almost 
excluded  from  the  upper  parts  of  the  river.  That  the  polluted  condition 
is  creeping  down  stream  is  shown  by  comparisons  of  collections  made  in 
1911  with  those  made  in  1918.  In  the  earlier  years  a  foul- water  fungus 
disappeared  from  the  river  near  Starved  Rock;  in  1918  it  was  found  at 
Henry  and  Lacon,  35  and  41  miles  farther  down  the  river  (Forbes  and 
Richardson,  1919:145).  At  the  present  time  (1919)  optimum  conditions 
and  a  normal  river  fauna  are  not  encountered  until  Peoria  is  reached,  a 
distance  of  about  120  miles  from  the  chief  source  of  pollution  at  Lockport. 
Sewage  from  the  towns  and  cities  along  the  river  also  contribute  to  the 
general  septic  condition. 

A  striking  example  of  the  deadly  effect  of  sewage  pollution  on  the 
mussel  life  of  a  stream  is  given  by  Wilson  and  Clark  (1912:34)  in  their 
study  of  the  Kankakee  River  mussel  fauna.  "The  DesPlaines  River, 
which  joins  the  Kankakee  to  form  the  Illinois  River,  is  simply  an  immense 
sewer  bringing  down  the  Chicago  sewage.  Both  rivers,  but  especially  the 
DesPlaines,  are  full  of  the  characteristic  algae  and  other  vegetation  which 
grow  in  such  waters^  and  the  combination  of  a  copious  vegetation  with  the 
sewage  has  effectually  killed  off  all  the  mussels  in  the  vicinity.  Not  a 
single  living  specimen  could  be  found  in  either  river;  but  there  were  hun- 
dreds of  dead  shells  along  the  banks,  most  of  these  old  and  well  bleached, 
but  still  capable  of  identification."    This  statement,  of  course,  applies  only 


167]  FAUNA  OF  BIG  VERM lUON  RIVER— BAKER  69 

to  the  lower  part  of  the  Kankakee  River  where  the  influence  of  the  polluted 
DesPlaines  has  worked  upstream  for  some  distance.  The  Kankakee  River 
for  the  most  part  is  a  highly  productive  stream  with  a  high  rate  of  dissolved 
oxygen,  in  fact,  the  water  is  supersaturated  with  this  life-giving  element. 

In  the  Maumee  River  (Wilson  and  Clark:1912,  26,  28)  shell  beds  were 
found  which  had  probably  been  killed  by  the  refuse  from  gas  works  near 
the  junction  of  the  St.  Mary's  and  St.  Joseph's  rivers.  "Spots  of  tar  were 
found  on  dead  mussels  some  distance  below  this  point.  The  water  was 
covered  with  an  oily  scum  in  places  and  a  tarry  odor  was  perceptible  for 
several  miles  down  the  river."  Lower  down  the  river  the  mussels  were 
showing  the  effect  of  increased  pollution  of  the  river  by  sewage. 

The  pollution  is  worst  and  usually  the  most  deadly  to  animal  life  during 
periods  of  low  water  and  in  winter  when  the  amount  of  water  in  the  stream 
is  small  and  the  decomposing  organic  material  has  less  water  to  deprive 
of  its  dissolved  oxygen.  During  times  of  floods  the  putrescent  material 
is  also  carried  down  the  stream  for  many  miles  and  contaminates  areas  not 
previously  affected. 

While  all  clean-water  forms  of  animal  life  are  more  or  less  affected 
by  sewage  pollution,  the  decomposition  of  organic  matter  abstracting 
dissolved  oxygen  from  the  water  and  rendering  it  unsuitable  for  aquatic 
life,  the  fish,  river  mussels  and  crayfish  are  particularly  affected,  most 
fish  being  especially  sensitive  to  contaminated  water.  Some  fish  (as  the 
brook  silversides,  Labidesthes  sicculus)  are  notably  sensitive,  while  others 
(as  the  black  bullhead,  Ameiurus  melas)  will  endure  water  that  is  badly 
polluted  (Shelford,  1918:27;  Wells,  1918:562-567).  The  young  fish  are 
relatively  more  sensitive  than  the  adult  fish.  It  is  noteworthy  that  the  more 
resistant  species  of  fish  are  inhabitants  of  sluggish  bodies  of  water,  as  ponds 
and  shallow  lakes,  while  the  least  resistant  species  live  in  running  streams. 
It  seems  to  be  a  question  of  the  amount  of  oxygen  necessary  for  the  well 
being  of  the  fish. 

The  ill  effect  of  sewage  pollution  is  most  marked  on  the  bottom  of 
bodies  of  water,  where  a  sludge  is  formed,  often  of  great  thickness  (as 
much  as  ten  feet  in  some  instances),  consisting  of  a  mass  of  soft,  black, 
sediment  with  a  high  content  of  organic  matter,  in  which  only  a  few 
organisms,  normally  inhabitants  of  polluted  streams,  can  live  (e.g.,  septic 
Protozoa  and  Rotifera,  foul- water  algae,  and  slime  worms,  Tubificidae). 
This  effect  on  the  bottom  is  perhaps  the  most  serious  phase  of  stream 
pollution  because  the  septic  condition  of  this  area  continues  in  operation 
long  after  the  original  source  of  contamination  ceases  to  operate.  This 
sludge  formation  renders  the  bottom  unfit  for  clean-water  life  upon  which 
many  fish  depend  for  food. 

The  effect  of  sewage  pollution  on  the  fish  population  of  the  upper  Illi- 
nois River  has  been  marked,  many  species,  such  as  catfishes,  red-horse. 


70  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [168 

buffalo,  and  sheepshead,  which  were  formerly  very  common  and  taken  in 
quantity  by  the  fishermen  several  years  ago,  are  now  either  wanting,  or 
greatly  reduced  in  numbers.  Other  fish,  not  bottom  feeders,  such  as 
sunfishes,  crappies,  and  the  basses,  are  reported  to  be  decreasing  in  recent 
years  as  polluted  conditions  are  creeping  down  the  river  (Forbes  and 
Richardson,  1913:544).  It  has  been  observed  that  fish  entering  a  polluted 
stream  from  a  clean-water  tributary  soon  die  if  unable  to  return  to  clean 
water.  The  fauna  of  a  polluted  stream  also  becomes  gradually  of  greater 
size  as  the  distance  from  the  source  of  pollution  increases.  This  has  been 
observed  by  Forbes  and  Richardson  in  the  Illinois  River,  by  Ortmann  in 
the  Allegheny  River,  and  by  the  author  in  the  Big  Vermilion  River. 
The  time  necessary  for  the  recovery  of  the  normal  biota  of  such  a  stream 
will  in  most  cases  be  of  long  duration  and  in  the  case  of  a  stream  polluted 
by  wastes  from  mines  and  chemical  manufacturies,  there  may  never  be  a 
return  to  the  original  condition. 

In  New  York  State,  the  Genesee  River,  at  Rochester,  has  afforded  a 
striking  example  of  stream  pollution,  of  the  efifect  of  this  pollution  on  cer- 
tain animal  life  in  the  river,  and  of  the  return  of  this  life  when  the  amount 
of  pollution  has  been  largely  reduced.  This  stream  has  been  under  observa- 
tion by  the  writer  for  a  period  of  twenty-seven  years  (1892  to  1919)  and 
collections  of  the  molluscan  life  have  been  made  from  time  to  time,  both 
before  the  period  of  maximum  pollution  and  since  that  time.  The  portion 
of  the  river  studied  lies  below  the  lower  falls  north  of  the  city,  and  about  a 
quarter  of  a  mile  below  the  outfall  of  several  trunk  sewers,  the  sewage 
being  discharged  into  the  river  in  a  crude  condition.  Refuse  and  other 
waste  matter,  both  liquid  and  solid,  also  enter  the  stream  from  gas  works, 
tanneries,  and  manufacturing  plants  above  the  lower  falls. 

Collections  made  in  1892,  before  pollution  became  notably  apparent, 
included  nine  species  of  gastropod  mollusks,  three  being  water  breathers 
and  six  air  breathers.     These  species  included: 

Musculium  transversum  Physa  sayii 

Musctdium  partumeium  Physa  oneida 

Bythinia  lentacidaUi  Galba  catascopium 

Planorbis  triwlvis  Galba  caperaia 
Physa  gyrina 

Individuals  were  notably  abundant,  thickly  covering  the  rocks  and 
the  shore.  In  1897,  it  was  observed  that  the  sewage  was  increasing  in 
volume  and  pollution  was  becoming  more  noticable,  the  water  appearing 
like  very  heavy,  greasy  dish  water.  The  river  was  visited  and  examined 
at  short  intervals  from  1898  to  1919.  Each  year  it  was  noted  that  pollu- 
tion was  rapidly  increasing.  In  1907,  the  water-breathing  mollusks, 
Musculium  and  Bythinia,  had  succumbed  and  none  could  be  found. 
The  air-breathers,  Galba,  Planorbis,  and  Physa,  still  held  out,  though 


169]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  71 

reduced  in  number  of  individuals.  An  examination  made  in  1910  failed 
to  discover  a  single  living  mollusk  of  any  species.  Apparently  the  water 
had  reached  such  a  state  of  concentrated  pollution  that  even  the  air-breath- 
ing mollusks,  which  normally  come  to  the  surface  to  take  free  air,  could 
not  adapt  themselves  to  this  unfavorable  environment  and  were  either 
killed  or  compelled  to  migrate  down  the  river  to  a  point  where  pollution 
was  less  deadly.  During  the  following  years,  1910  to  1913,  the  river  was 
visited  but  no  mollusks  were  found. 

Duritig  the  summer  of  1912,  G.  C.  Whipple,  made  a  study  of  the  effect 
of  the  sewage  pollution  on  certain  animal  and  vegetal  life  in  the  Genesee 
River  (Fisher,  1913:179-200).  This  study  was  made  when  pollution  was 
at  its  maximum  and  during  the  period  when  molluscan  life  had  disappeared 
from  the  lower  part  of  the  river.  The  dissolved  oxygen  in  the  lower  river, 
below  the  trunk  line  sewer,  in  July  and  August,  when  the  temperature 
was  high  and  the  water  low,  varied  from  5  to  41  per  cent  of  saturation. 
The  water  at  the  bottom  of  the  river  almost  always  contained  less  oxygen 
than  that  at  the  surface.  On  one  day  in  August,  the  percentage  of  satu- 
ration in  a  distance  of  three  miles  did  not  exceed  5  per  cent  from  the 
surface  to  the  bottom  of  the  stream,  which  has  a  depth  of  about  twenty- 
six  feet.  The  number  of  bacteria  per  cc  for  this  period  was  1,650,000  near 
the  source  of  pollution  and  but  67,000  per  cc  near  the  mouth  of  the  river 
where  the  influence  of  the  pure  water  from  Lake  Ontario  increased  the 
amount  of  dissolved  oxygen. 

In  1917,  a  large  part  of  the  city  sewage  was  diverted  to  a  disposal 
plant  situated  near  the  shore  of  Lake  Ontario.  Here  an  average  of  32 
million  gallons  of  sewage  are  treated  daily  and  the  treated  sewage  is  dis- 
charged into  Lake  Ontario  in  deep  water  at  some  distance  from  shore. 
It  is  at  once  apparent  that  when  this  large  amount  of  sewage  was  discharged 
into  the  Genesee  River  in  a  crude  condition,  it  could  not  but  render  the 
water  totally  unfit  for  animal  life  and  a  menace  even  to  the  inhabitants 
who  visited  the  beautiful  parks  bordering  both  sides  of  the  lower  Genesee 
River. 

The  result  of  the  diminution  in  the  amount  and  character  of  the  sewage 
discharged  into  the  river  has  been  that  the  molluscan  fauna,  as  well  as 
other  forms  of  aquatic  animal  life,  have  returned  and  are  rapidly  taking 
possession  of  the  favorable  environments  which  were  in  use  previous 
to  the  maximum  period  of  pollution.  Collections  made  in  September, 
1919,  contained  six  species,  two  being  water-breathers  and  four  air- 
breathers. 

Musculium  transversum  Planorbis  trivohis 

Bythinia  tentaculala  Pkysa  integra 

Galba  catascopium  Physa  oneida 


72  JLUNOIS  BIOLOGICAL  MONOGRAPHS  [170 

It  will  be  noted  that  of  the  returned  species,  one  is  different  (Physa  integra), 
while  four  are  missing,  Galba  caperata,  Physa  gyrina,  Physa  sayii,  and 
Musculium  partumeium.  It  frequently  happens  that  when  a  fauna  returns 
to  a  habitat  from  which  it  has  been  driven  by  unfavorable  conditions,  it 
is  made  up  of  a  different  aggregation  of  species  (see  Ortmann,  1909,  for 
additional  notes  on  this  subject). 

The  Genesee  River  is  a  striking  example  of  the  history  of  a  polluted 
stream  and  its  effect  on  one  group  of  animal  life.  Previous  to  the  stage 
of  greatest  pollution  there  is  a  varied  fauna  of  mollusks  very  numerous  in 
individuals.  In  the  course  of  eleven  y^ars  the  gill-bearing  species  are 
forced  out  and  after  a  lapse  of  fourteen  years  all  molluscan  life  ceases  to 
live  in  this  part  of  the  river.  Seven  years  later  the  greater  amount  of 
sewage  is  diverted  to  another  outlet.  Two  years  after  this  change  the  mol- 
lusks have  returned  in  as  great  numbers  as  before  the  maximum  stage  of 
pollution.  The  significance  of  all  this  lies  in  the  fact  of  the  early  return  of 
this  life  and  strikingly  indicates  that  streams  may  become  restocked  with 
life  in  a  short  period  after  pollution  has  ceased  to  be  of  an  unfavorable 
character,  provided,  of  course,  the  bottom  of  the  stream  has  not  been 
made  permanently  untenable  by  the  deposition  of  poisonous  substances 
that  cannot  be  washed  away  by  ordinary  river  currents.  It  is  quite  prob- 
able that  the  large  fall  of  water,  some  60  feet  in  height,  immediately  above 
the  sewage  outlet,  has  had  a  marked  effect  in  the  return  of  these  favorable 
conditions. 

No  additional  data  are  at  hand  indicating  the  changes  in  a  polluted 
stream  after  septic  conditions  have  ceased  or  become  greatly  modified. 
It  is  probable  that  similar  beneficial  results  would  be  obtained  in  other 
streams  if  the  sewage  was  diverted  or  treated  to  remove  the  large  amount 
of  organ,ic  matter.  In  the  case  of  a  stream  like  the  Salt  Fork,  the  septic 
<;ondition  of  which  will  be  discussed  in  the  following  pages,  it  would 
probably  not  require  a  very  long  time  to  reduce  the  septic  conditions  if 
the  sewage  from  Urbana  and  Champaign  were  properly  treated.  While 
the  putrescible  matter  at  present  covers  everything,  in  some  places  to  a 
considerable  depth,  the  high  water  during  the  spring  would  in  several 
seasons  remove  a  large  part  of  this  material,  and  if  no  additional  matter 
was  permitted  to  flow  into  the  stream,  the  lapse  of  a  few  years  would 
enable  nature  to  bring  the  stream  back  to  a  normal,  healthy  condition, 
and  make  it  a  place  to  seek  for  recreation  instead  of  a  place  to  avoid  on 
account  of  its  filth,  as  at  present. 

SEWAGE  POLLUTION  IN  THE  SALT  FORK 

The  sewage  and  other  wastes  of  the  Twin  Cities  of  Urbana  and  Cham- 
paign are  discharged  into  the  waters  of  the  Salt  Fork  by  separate  systems, 
that  of  Urbana  emptying  into  the  Boneyard  near  the  Big  Four  shops,  while 


171]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  73 

the  sewer  outlet  of  the  Champaign  system  is  situated  on  the  Salt  Fork 
about  a  mile  below  th,e  Urbana  outlel;.  There  are  two  systems  for  each 
city,  one  for  domestic  wastes  and  the  other  for  the  care  of  storm  water, 
the  sanitary  sewage.  Septic  tanks  were  installed  with  the  systems,  about 
the  year  1894,  to  reduce  the  amount  of  putrescible  matter,  but  at  the  pres- 
ent time  the  sewage  receives  little  treatment  and  practically  enters  the 
Salt  Fork  in  a  crude  condition.*  The  population  in  1914  was  estimated  to 
be  13,750  for  Champaign,  and  9,252  for  Urbana,  or  a  total  population  of 
about  23,000  for  the  Twin  Cities.  At  the  present  time,  1920,  six  years  later, 
the  increase  has  probably  brought  the  total  up  to  nearly  30,000.  The 
sewage  system,  therefore,  provides  disposal  for  this  population,  and  is  all 
discharged  into  the  waters  of  the  Salt  Fork.  It  is  estimated  by  G.  C.  Haber- 
meyer,  that  the  total  flow  of  sewage  from  the  Urbana  plant  is  about  500,000 
gallons  per  day  and  from  the  Champaign  plant  about  1,000,000  gallons 
per  day.** 

The  flow  of  the  Salt  Fork  below  the  Champaign  sewage  disposal  plant 
is  3,000,000  gallons  per  day.  These  figures  indicate  that  the  sewage  forms 
one-half  of  the  total  water  flowing  down  the  Salt  Fork.  These  data  were 
taken  in  October,  when  the  stream  was  low,  and  may  be  a  trifle  too  high 
for  those  periods  when  there  is  a  rise  of  water  following  a  period  of  rainy 
weather.  During  a  greater  part  of  the  year,  however,  the  water  is  low  and 
these  figures  will  be  approximately  correct.  The  fresh  water  added  to 
the  sewage  is  derived  from  the  stream  north  of  Urbana  which  contributes 
250,000  gallons  per  day,  and  the  Boneyard,  which  adds  1,500,000  gallons 
per  day,  about  two-thirds  being  clear  water.  "In  October,  1917,  the 
flow  in  the  Boneyard  below  the  Urbana  tank  was  about  one-third  sewage 
and  probably  contained  considerable  other  waste  and  sewage  discharged 
above  the  Urbana  sewage  outlet.  The  flow  in  Salt  Fork  below  the  Cham- 
paign sewer  outlet  was  probably  one-half  sewage." 

H.  E.  Babbitt,***  thus  describes  the  condition  at  the  Champaign  dispo- 
sal plant  at  this  date.  "The  appearance  of  the  effluent  from  the  Champaign 
septic  tank  is  that  of  fresh  sewage,  having  the  typical  color  of  sewage,  and 
carrying  fecal  matter  and  paper.  The  appearance  of  the  Salt  Fork  at  the 
point  of  entrance  of  the  sewage  from  the  tank  is  good.    It  is  about  twenty 

*  New  septic  tanks  have  been  installed  at  the  Champaign  sewage  disposal  plant  on  Salt 
Fork  and  a  portion  of  the  sewage  is  well  treated  before  it  enters  the  canal. 

**  Data  for  the  sewage  conditions,  stream  flow,  chemical  analyses,  etc.,  of  the  Salt  Fork  are 
taken  from  an  unpublished  report  of  G.  C.  Habermeyer  (assisted  by  S.  D.  Kirkpatrick,  assis- 
tant chemist,  and  J.  F.  Schellbach,  engineer)  made  for  the  State  Water  Survey  Division  of 
the  Department  of  Registration  and  Education,  of  Illinois,  and  here  used  by  permission  of  the 
late  Chief  of  the  Division,  Dr.  Edward  Bartow. 

***  From  unpublished  Report  on  the  Champaign-Urbana  Water  Works  System,  prepared 
June  23,  1914.    Extracts  here  published  by  permission  of  Edward  Bartow. 


74  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [172 

feet  wide,  fifteen  to  eighteen  inches  deep,  clear,  colorless,  and  odorless. 
The  stage  of  water  at  the  time  of  inspection  was  low.  No  septic  action 
was  present  except  in  the  open  ditch  through  which  the  sewage  flows  from 
the  tank  into  the  stream.  There  is  a  large  sludge  bank  in  the  stream 
immediately  below  the  outlet  and  a  most  obnoxious  odor."  Effluent  from 
the  Urbana  tank  appeared  as  typical  fresh  sewage,  but  was  not  representa- 
tive of  the  ordinary  effluent  as  the  tank  had  been  cleaned  only  the  day 
previous  to  the  visit  (page  9). 

The  stream  known  under  the  name  of  the  ''Boneyard"  carries  both 
waste  and  sewage.  This  stream  is  about  three  and  a  half  miles  in  length  and 
rises  about  half  a  mile  beyond  the  northern  limits  of  the  City  of  Cham- 
paign. The  stream  flows  southward  to  near  Third  and  Green  streets, 
where  it  abruptly  turns  eastward,  emptying  into  the  Salt  Fork  near  the 
Big  Four  shops  in  Urbana.  This  stream  has  a  drainage  area  of  about  eight 
and  a  half  square  miles.  Sewage  enters  the  Boneyard  near  Goodwin 
Avenue  and  at  the  old  high  school  on  Stoughten  Street,  Urbana.  Water 
bearing  wastes,  presumably  from  business  houses  near  by,  enters  the  stream 
north  of  Main  Street.  The  banks  close  to  the  water  line  near  Main  Street 
culvert  are  slimy  and  green  (data  from  G.  C.  Habermeyer,  1918). 

The  Boneyard  is  subject  to  great  fluctuations  of  water  level,  due  to  the 
severe  storms  of  spring  and  summer  when  heavy  rains  occur.  At  such  times 
a  rise  of  three  or  four  feet  in  a  few  hours  is  not  unusual  and  the  waters 
overflow  all  adjacent  low  land.  At  one  time  (reported  very  bad  in  1915) 
chemical  wastes  in  the  form  of  oil  and  tar  were  discharged  into  the  stream 
from  the  gas  works  of  the  Champaign  Street  Railway,  Gas  and  Electric 
Company,  situated  at  the  comer  of  Fifth  and  Hill  streets,  Champaign, 
east  of  the  Illinois  Central  tracks.  The  oil  at  one  period  extended  the 
entire  length  of  the  Boneyard,  covering  lawns,  when  the  water  was  high, 
with  an  unsightly  layer  of  heavy  oil.  The  shores  and  bottom  of  the  stream 
in  many  places  were  covered  with  tar,  which  has  not  subsequently  been 
removed  and  also  cannot  be  removed  by  the  natural  flow  of  water,  but  must 
be  artificially  taken  from  the  stream  bed.* 

The  oil  discharged  from  the  gas  works,  as  well  as  from  some  other 
points  along  the  Boneyard,  is  absolutely  inimical  to  any  life  in  the  stream. 
The  tar,  if  carried  down  stream,  finally  settles  to  the  bottom  and  unless 
artificially  removed,  will  remain  there  and  render  the  stream  unfit  for 
bottom  inhabiting  life  of  any  kind.  Fortunately,  such  pollution  is  confined 
to  the  upper  part  of  the  Boneyard.  Waters  charged  with  sewage  may 
become  purified  in  a  year  or  two  after  pollution  ceases,  but  they  will  sel- 
dom or  never  recover  from  chemical  pollution  such  as  is  produced  by  tar 

*  From  Ralph  Hilscher,  Report  on  Contamination  of  the  Boneyard  in  Champaign  by 
Gas  House  Wastes  August  28, 1915.   Here  published  by  permission  of  Edward  Bartow. 


1731  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  75 

and  similar  wastes.  Ortmann's  work  on  the  rivers  of  western  Pennsylvania 
clearly  indicate  the  baneful  results  of  such  pollution  (Ortmann,  1909). 

The  Boneyard  is  apparently  now  barren  of  all  clean  water  life.  Fre- 
quent examinations  made  during  1918  failed  to  supply  any  life  of  this 
character.  Fresh  water  pulmonate  mollusks,  and  Cambarus  and  other 
smaller  Crustacea  were  once  abundant,  but  appear  to  be  wanting  at  the 
present  time.  A  large  snapping  turtle  was  observed  in  the  Boneyard  near 
Lincoln  Avenue,  in  1918.  The  ditched  portion  of  Salt  Fork  above  Urbana, 
is  a  clean  water  stream,  filled  with  aquatic  life,  which  abruptly  terminates 
at  the  junction  of  this  stream  with  the  Boneyard,  with  its  load  of  sewage 
from  Urbana.  From  here  to  a  point  fourteen  miles  below  Urbana  not  a 
living  mussel  was  found,  and  no  air  breathing  snails  were  observed,  except 
in  one  instance,  believed  to  have  been  introduced  from  a  near-by  portion 
of  the  old  river  bed,  which  still  retains  clean  water  life,  above  St.  Joseph, 
a  distance  of  ten  miles  below  Urbana.  The  large  number  of  empty  valves 
and  paired  shells  of  the  river  mussels  below  St.  Joseph  indicate  an  environ- 
ment that  has  become,  more  or  less  recently,  inimical  to  these  creatures. 
Crayfish  were  also  absent  from  the  same  area. 

Habermeyer's  report  of  Salt  Fork,  October  1,  1917,  describes  condi- 
tions as  follows:  "The  stream  below  the  Champaign  outlet  to  the  north 
line  of  section  10,  one  and  a  half  miles  below  the  outlet,  was  in  very  foul 
condition.  At  the  east  line  of  section  11,  four  miles  below  the  Champaign 
sewer  outlet,  the  stream  appeared  to  be  quite  clear  and  there  was  no 
offensive  odor  noticeable.  At  the  outlet  of  the  west  branch  of  Salt  Fork, 
the  water  was  clearer  than  that  in  the  north  branch  (Spoon  River).  A 
resident  near  the  junction  of  the  two  branches  stated  that  at  times  when 
the  creek  flow  increased,  foul  matter  was  washed  down  from  above  and 
there  was  considerable  odor  in  the  vicinity  for  a  day  or  two." 

The  dredging  of  a  new  channel  has  been  responsible  for  the  water 
being  clearer  at  times  in  Salt  Fork  than  in  Spoon  River,  providing  a  sand 
bottom  which  is  hard  and  resistant  and  has  not  yet  silted  up  to  any  degree. 
Spoon  River  has  a  mud  bottom  and  the  waters  are  turbid  a  large  part  of 
the  time.  In  a  photograph  of  the  Salt  Fork  taken  some  eight  miles  below 
Urbana  (two  miles  northwest  of  St.  Joseph),  the  water  was  so  clear  that 
the  ripple  marks  on  the  sandy  bottom  may  be  distinctly  seen  in  the  picture 
(Fig.  45)  yet  the  stream  at  this  point  was  totally  barren  of  clean  water 
life  and  the  water  was  laden  with  masses  of  decomposing  matter,  made  up 
of  foul  water  algae  and  Protozoa,  and  the  bottom  was  filled  with  slime 
worms  (Limnodrilus) .  Below  the  junction  of  these  two  branches,  bottom 
conditions  are  still  very  bad,  and  clean  water  life  does  not  appear  for  a 
distance  of  several  miles,  as  has  already  been  shown. 

The  people  mentioned  in  the  report  were  interviewed  in  1918.  They 
reported  that  no  trouble  was  experienced  during  periods  of  low  water,  but 


76  ILUNOIS,BIOLOGJCAL  MONOGRAPHS  [174 

that  after  rains,  when  the  stream  rapidly  rose,  putrescible  matter  was 
washed  down  stream,  cast  on  shore,  and  the  odor  was  then  very  bad.  This 
lasted  until  the  water  subsided.  In  the  fall  of  1920,  the  same  people  were 
again  interviewed  and  conditions  were  reported  to  be  much  worse  than 
previously,  the  unusually  low  stage  of  the  water  causing  the  putrescible 
matter  to  decay  on  the  exposed  sand  bars  in  the  river,  from  which  some 
odor  was  noticed. 

Stream  measurements  of  the  velocity  of  the  current  were  made  by  the 
Water  Survey  at  several  points  along  the  Salt  Fork.  These  were  made  by 
Habermeyer  on  October  1,  1917,  when  the  water  was  low  in  the  stream. 
All  data  given  in  feet. 

Table  IX.    Mouth  of  the  Bonzyakd 

Distance  from  east  bank 1                           2,  3 

Depth  of  water 0.6                       0.7  0.4 

Flow  per  hour 4608                     4500  4320 

Salt  Fork,  Four  Miles  below  Champaign  Sewer  Outlet 

Distance  from  bank 2.9                2.4                1.8  2.2 

Flow  per  hour 3888             4320             4212  2412 

These  measurements  indicate  a  very  slow  current,  from  about  one  half 
to  nearly  a  mile  an  hour.  At  high  water  the  rate  of  flow  is  undoubtedly 
several  times  as  great.  This  slow  rate  of  flow  would  cause  much  of  the 
heavy  matter  in  the  sewage  to  be  precipitated  to  the  bottom  and  form 
sludge  banks,  and  this  has  occurred  at  many  places  below  both  the  Urbana 
and  Champaign  outlets.  High  water  and  more  rapid  current  probably 
moves  some  of  this  sludge  farther  down  stream,  also  carrying  the  fresh 
sewage  farther  down  at  such  times.  A  recent  examination  made  at  very 
low  water  indicates  that  this  has  been  the  case,  for  hundreds  of  bars  were 
observed  out  of  water,  each  covered  with  a  sludge  formation  of  greater 
or  less  size. 

Analyses  of  water  from  various  places  in  the  Salt  Fork  and  tributary 
streams  have  been  made  by  the  Water  Survey.  The  two  tables  that  fol- 
low, taken  from  Habermeyer's  report,  indicate  some  of  the  conditions  of 
the  upper  waters  of  Salt  Fork  (Tables  X  and  XI). 

In  Table  X  the  low  percentage  of  dissolved  oxygen  (saturation)  in 
the  ditched  stream  above  Lincoln  Avenue  is  noteworthy  as  compared  with 
the  larger  amount  at  Cunningham  Avenue.  At  both  localities,  however, 
the  water  is  relatively  pure,  there  being  little  or  no  pollution.  The  sample 
from  a  mile  and  a  quarter  below  the  champaign  outlet  is  striking  because 
of  the  total  absence  of  oxygen.  The  sudden  rise  in  saturation  at  four 
and  eight  miles  is  also  notable,  and  indicates  that  at  these  points  on  this 
date  little  decomposition  was  taking  place.  The  sample  from  Salt  Fork 
near  Spoon  River  shows  a  marked  fall  in  the  amount  of  dissolved  oxygen, 


175J 


FAUNA  OP  BIG  VERMILION  RIVER 


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177]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  19 

which  coincides  with  the  absence  of  mollusks  and  crayfish  from  this  part  of 
the  stream.  The  rise  of  the  oxygen  content  200  feet  upstream  in  Spoon 
River  shows  the  effect  of  the  cleaner  water,  and  this  also  coincides  with 
the  presence  of  clean  water  life  in  this  part  of  Spoon  River.  The  lower 
temperatures  were  probably  responsible  for  the  rise  in  oxygen  content  at 
the  stations  four  and  eight  miles  below  Urbana.  In  the  summer  months, 
during  low  water  and  high  temperature  conditions,  the  percentage  would 
probably  be  much  lower.  This  difference  was  noted  by  Forbes  and 
Richardson  in  their  study  of  the  Illinois  River.  The  percentages  of  dis- 
solved oxygen  are  relatively  higher  in  these  two  stations  of  the  Salt  Fork, 
four  and  eight  miles  from  the  source  of  pollution,  than  in  the  Illinois  River 
at  Starved  Rock,  Hennepin,  and  Chillicothe,  where  samples  taken  in  Octo- 
ber showed  smaller  percentages,  though  many  miles  from  the  chief  source 
of  pollution  at  Lockport  (Forbes  and  Richardson,  1913:565). 

The  rise  and  fall  in  the  number  of  bacteria  and  the  presence  of  many 
gas-forming  organisms  in  the  Salt  Fork  is  well  shown  in  the  table.  The 
sudden  rise  from  Cunningham  Avenue  to  the  point  one  and  a  quarter 
miles  below  the  Champaign  sewer  outlet  is  very  striking  and  indicates 
in  a  graphic  manner  the  difference  between  clean  water  and  that  heavily 
polluted  by  sewage  wastes.  The  high  number  200  feet  up  from  the  mouth 
of  Spoon  River  indicates  that  there  is  some  pollution  in  this  stream,  al- 
though not  far  above  this  point  living  mollusks  (Naiades)  were  found  in 
abundance. 

In  Table  XI,  the  relative  high  amounts  of  albuminoid  nitrogen,  as  well 
as  ammonia  nitrogen,  supplied  by  the  sewage  material,  in  contrast  with  the 
small  amounts  in  the  purer  water  of  the  stream,  are  strikingly  shown. 
All  of  these  agencies  are  inimical  to  clean  water  life,  especially  fish,  mussels, 
and  crayfish,  which  by  their  relative  abundance  or  absence,  indicate  in  a 
most  satisfactory  manner  the  quality  of  the  environment,  and  its  fitness 
for  the  well-being  of  its  inhabitants. 

The  sewage  in  the  Salt  Fork  has  greatly  increased  in  recent  years,  fol- 
lowing the  increase  in  population,  and,  as  in  the  case  of  the  sewage  from 
Chicago  in  the  Illinois  River,  the  polluted  condition  is  gradually  creeping 
down  the  stream  below  St.  Joseph,  changing  the  pure  water  inhabitants 
to  those  that  can  live  under  septic  conditions.  As  no  collections  were  made 
during  previous  years  from  the  stream  below  St.  Joseph  it  is  not  now  pos- 
sible to  make  comparisons  of  the  present  with  previous  conditions.  Such 
lists  as  have  been  available  have  not  indicated  precisely  the  location  from 
which  they  were  collected  (as  in  the  neighborhood  of  St.  Joseph,  which 
might  mean  in  the  Salt  Fork  or  in  Spoon  River)  and  they  cannot  be  used 
for  this  reason.  The  value  of  exact  local  lists  is  emphasized  in  studies  of  this 
kind,  showing  that  strictly  technical  (or  pure  science)  information  is  often 
of  the  greatest  value  in  the  study  of  economic  probems. 


80  ILUNOIS  BIOLOGICAL  MONOGRAPHS  (178 

RECENT  EXAMINATION  OF  THE  POLLUTED  PORTION  OF  SALT  FORK 

Figures  21,  36  to  45 

During  the  fall,  winter,  and  spring  of  1919  and  1920  Salt  Fork  was 
carefully  examined  from  Urbana  to  St,  Joseph.  All  parts  of  the  stream 
were  searched  for  macroscopic  life  and  samples  of  the  bottom  and  of  the 
water  were  taken  for  microscopic  study,  to  determine  the  character  and 
abundance  of  the  foul-water  organisms  present.  Examinations  were  made 
during  the  months  of  May,  September,  October,  November,  and  December. 

During  the  spring  months  the  water  is  so  high  in  the  stream  that  collec- 
tions can  not  be  made  and  examination  of  the  water  is  difficult.  The 
great  volume  of  water,  laden  with  both  sewage  and  silt,  is  of  a  dark  lead 
color  and  polluted  conditions  are  not  apparent,  although  some  putrescent 
matter  was  observed  on  several  occasions.  In  the  fall  months  conditions 
are  much  more  favorable  for  critical  examination,  the  water  being  so  low 
that  one  may  wade  over  any  part  of  the  stream.  It  is  at  this  time,  which 
extends  from  July  through  the  fall  and  winter  to  the  rainy  period  in  March 
or  April,  that  the  polluted  conditions  are  very  apparent  and  the  most 
satisfactory  studies  can  be  made.  The  general  conditions  of  the  stream  at 
this  period  are  summarized  below. 

The  water  in  the  Boneyard  near  the  Big  Four  shops,  below  the  Urbana 
sewage  outlet  is  usually  shallow,  from  a  foot  or  less  to  two  feet  in  places. 
The  bottom  is  a  mass  of  sludge  with  putrescent  material  covering  all 
objects  in  the  water  and  floating  down  the  stream,  which  has  an  estimated 
flow  of  about  half  a  mOe  an  hour.  Several  large  sludge  banks  are  exposed 
and  the  odor  is  usually  nauseating  (Fig.  39).  At  the  junction  of  the 
Boneyard  with  the  Salt  Fork  the  water  varies  from  six  inches  to  a  foot 
in  depth,  there  are  several  sludge  banks  and  the  putrescent  matter  covers 
all  objects  and  lines  the  shores  to  a  height  of  several  feet,  indicating  former 
high  water  marks  (Fig.  36).  Samples  of  the  sludge  and  green  putrescent 
material  from  one  of  these  sludge  banks  were  examined  by  Professors 
Smith  and  Transeau  and  the  following  algae,  Protozoa  and  other  animals 
observed: 

Blue-green  algae  Animals 

Pediastrum  simplex,  common.  Paramoecium,  not  common. 

Senedestnus  abundans,  rare.  Euglena  geniculata,  very  abundant. 

Phormidium  inundatum,  abimdant  Limnodrilus  (sludge  worm) ,  very  abiin- 

Diatoms  danL 

Namcula  cryptocephala,  common.  Tubifex  (sludge  worm),  one  specimen. 

Synedea  pulchella,  not  common.  Nematode  worms,  several. 

Ciliate  Protozoa  were  numerous,  including  Colpodium  and  a  few 
hypotrichous  and  peritrichous  species. 


179]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  81 

At  the  junction  of  the  Boneyard  with  the  Salt  Fork  the  waters  of  the 
two  streams  usually  formed  two  distinct  bands,  the  clear  water  of  the  latter 
on  the  left  or  north  bank  and  the  murky,  sewage-laden  water  of  the  Bone- 
yard  on  the  right  or  south  bank,  the  line  in  the  center  of  the  stream  dividing 
the  two  waters  being  clearly  marked.  (Fig.  21).  The  waters  of  these 
two  streams  do  not  fully  mingle  until  they  have  flowed  a  distance  of 
several  hundred  yards.  All  the  way  down  the  Salt  Fork,  however,  as  far 
as  the  first  bridge,  the  right  side  is  more  discolored  than  the  left  side, 
indicating  that  the  sewage-laden  waters  of  the  Boneyard  and  Champaign 
outlet  flow  mostly  on  this  side  of  the  stream. 

At  the  Champaign  sewage  outlet,  about  half  a  mile  below  the  Bone- 
yard, there  is  usually  a  good  flow  of  water  from  the  discharge  pipe  into  an 
open  ditch,  which  empties  into  the  Salt  Fork  a  short  distance  away.  At 
the  point  of  entrance  of  the  open  ditch,  the  chocolate-colored  water  of  the 
Champaign  sewage  is  clearly  marked  as  a  dark  band  extending  around  the 
upstream  end  of  a  large  sludge  bank,  similar  to  the  one  described  in  Haber- 
meyer's  report  in  1917  (Fig.  41).  Some  fecal  matter  is  generally  pre- 
sent. The  water  in  the  Salt  Fork  at  this  point  is  usually  less  than  a  foot 
deep  and  the  bottom  is  made  up  of  a  soft  sludge  which  covers  everything  in 
the  water.    The  odor  is  very  bad,  almost  nauseating. 

Below  the  Champaign  outlet  the  stream  is  in  very  foul  condition,  as 
noted  in  Habermeyer's  report.  From  the  outlet  to  the  first  bridge,  more 
than  a  mile  down  stream,  the  water  is  less  than  a  foot  deep,  in  most  places 
but  a  few  inches,  and  the  bottom  has  much  sludge,  and  putrescent  matter 
covers  every  object  in  the  water,  as  well  as  the  shores  and  all  objects  on  the 
shores  to  a  height  of  several  feet,  indicating  former  stream  levels.  Fecal 
matter,  in  dark  brown  masses,  as  well  as  partly  decomposed  organic  matter 
colored  green  by  the  presence  of  blue-green  algae  and  the  protozoan 
Euglena,  are  usually  floating  down  the  stream.  The  bottom  substratum 
is  of  sand  and  gravel,  and  over  this  sludge  banks  have  been  formed  of 
greater  or  less  thickness.  Bars  of  sand  and  gravel  occur  at  irregular  inter- 
vals and  are  covered  with  masses  of  putrescent  matter  forming  long,  alter- 
nating streaks  of  black  and  green.  An  oily  scum  resembling  petroleum 
covers  the  surface  in  many  places,  and  the  bottom,  when  disturbed,  emits 
an  oily  substance  which  spreads  over  the  surface  as  an  oily  scum.  This  may 
represent  some  gas  house  wastes  as  well  as  heavy  oil  from  other  places 
along  the  Boneyard.  The  odor  in  this  section  of  the  stream  is  almost  over- 
powering in  many  places,  being  distinctly  a  privy  smell.  In  one  place  the 
observer  was  compelled  to  leave  the  vicinity  of  the  stream,  the  odor  was 
so  strongly  nauseating.  In  places,  bubbles  of  gas  may  be  seen  to  break  at 
the  surface  from  submerged  sludge  banks. 

Samples  of  the  bottom  sludge  and  putrescent  matter  floating  in  the 
water  were  collected  just  above  the  bridge,  about  a  mile  and  a  quarter 


82 


ILUNOIS  BIOLOGICAL  MONOGRAPHS 


[180 


below  the  Champaign  outlet.  Algae  and  animal  life  were  noted,  but  not  as 
abundantly  as  in  the  sludge  bank  at  the  junction  of  the  Salt  Fork  and  Bone- 
yard  (Fig.  21). 


Animals 
Euglena  genictdala,  very  few. 
Paramoecium,  one  specimen. 
Vorticella,  very  few. 


BluQ-green  algae 
Phormidium  inundatum,  abundant. 

Diatoms 
Navictda  salinarum,  abundant. 


The  scarcity  of  microscopic  life  and  the  total  absence  of  clean-water 
life  is  paralleled  by  the  chemical  condition  of  the  water  at  this  station, 
where  the  examination  of  samples  showed  a  total  absence  of  dissolved 
oxygen  and  the  presence  of  multitudes  of  bacteria  and  gas-forming  organ- 
isms (see  Tables  X,  XI). 

From  the  first  iron  bridge  to  the  Brownfield  woods  bridge,  a  distance 
of  about  a  mile  and  a  quarter,  the  stream  is  very  shallow,  less  than  a  foot 
in  depth  on  the  average,  the  water  grayish  with  a  sloppy  appearance,  and 
the  odor  foul  in  places,  though  not  as  nauseating  as  below  the  first  bridge. 
Putrescent  masses  of  soft,  grayish-black  or  greenish  matter,  ranging  in  size 
from  a  penny  to  a  platter,  may  be  seen  floating  down  stream,  held  together 
by  algal  strands.  Brown  masses  observed  on  shore  resembled  human  ex- 
crement. The  oily  appearance  of  the  surface  of  the  water  continues  and 
oily  matter  ascends  when  the  bottom  is  disturbed. 

From  the  Brownfield  bridge  to  the  third  (farmer's)  bridge,  a  distance 
of  about  three-quarters  of  a  mile,  the  conditions  are  the  same  as  above  this 
bridge  (Fig.  38).  Between  the  third  bridge  and  the  Cotton  woods  road 
bridge,  a  distance  of  about  a  mile,  the  water  is  very  shallow,  scarcely 
exceeding  six-inches  in  depth,  with  gravel  or  sand  bottom.  Sludge  bars, 
of  sand  mixed  with  organic  matter,  are  frequent,  in  many  places  occupying 
more  than  half  the  width  of  the  stream,  the  channel,  a  few  inches  to  a  foot 
in  depth,  meandering  over  the  bottom  between  these  bars  (Fig.  40). 

These  bars  presented  a  striking  appearance,  the  stones  and  sand  being 
black  from  the  decomposing  organic  matter,  and  the  foul  water  algae 
being  arranged  in  long  streaks,  presenting  in  combination  a  striped  green 
and  black  design.  The  green  algae  is  here  very  abundant,  floating  in  the 
stream  or  covering  the  shores.  In  places  the  encrusting  material  on  the 
shore  margins  is  bright  yellow.  Everywhere  along  the  stream  the  exposed 
surface  of  the  bottom  is  black  from  the  decomposing  organic  matter, 
which  covers  all  objects  and  has  been  baked  hard  by  the  hot  summer's 
sun.  The  vegetation  bordering  the  shore  also  shows  the  efi"ect  of  sewage 
action,  being  either  black  in  color  or  having  the  dried  pieces  of  polluted 
material  attached  to  the  lower  part  of  the  plants.  The  same  conditions 
prevail  from  the  Cottonwoods  road  to  the  Mayview  road,  a  distance  of 
about  two  miles. 


181]  FA  UNA  OF  BIG  VERMIUON  RIVER— BAKER  83 

Collections  of  materials  made  just  below  the  third  farmer's  bridge,  about 
three  and  a  half  miles  below  the  Champaign  outlet,  contained  the  following 
organisms: 

Blue-green  algae  Animals 

Phormidium  inundatum,  abundant.  Flagellate  Protozoa,  very  minute. 

Diatoms  Euglena  geniculata,  very  abundant. 

Navicula  salinarum,  abundant.  Many  in  stage  of  encystment. 

Dineutes  assimilis,  very  abundant. 

On  the  surface  of  the  water. 

Collections  at  the  Cottonwoods  bridge  (Fig.  42)  contained  a  larger 
variety  of  animal  life,  which  was  rather  meagerly  represented  above 
this  bridge.  This  place  is  on  the  east  line  of  section  11,  about  four  miles 
below  the  Champaign  outlet.    The  bottom  here  is  of  fine  sand  and  mud. 

Blue-green  algae  Animals 

Phormidium  inundatum,  abundant.  Euglena  geniculata,  very  abundant. 

Diatoms  Rotifer,  illoricate,  one  specimen. 

Navicula  salinarum,  abundant.  Limnodrilus,  two  specimens. 

Dineutes  assimilis,  a  few  examples. 

Mussel  shells  or  other  mollusks  were  entirely  absent  in  a  living  state 
and  their  shells  were  notably  rare.  About  three  quarters  of  a  mile  below 
the  first  bridge  east  of  Urbana,  a  half  valve  of  Lampsilis  luteola  was  found 
on  a  sand  bar  (Fig.  37).  Near  the  Brownfield  woods  bridge  many  broken 
pieces  of  mussel  shells,  as  well  as  a  few  mutilated  half  valves,  were  ob- 
served. At  a  farmer's  bridge  half  a  mile  below  this  bridge  several  broken 
valves  of  Lampsilis  luteola  and  Anodonta  grandis  were  collected,  (Fig. 
38)  and  from  this  point  down  stream  to  the  Cottonwoods  road  bridge 
detached  valves  or  broken  pieces  of  shell  were  more  or  less  common. 
From  observations  of  this  and  other  partfe  of  the  stream  it  seems  evident 
that  these  mutilated  shells  were  washed  from  the  spoil  banks  on  either  side 
or  from  the  bed  of  the  old  stream  channel  where  it  crosses  the  canal.  At  the 
junction  of  the  Boneyard  with  the  Salt  Fork  a  layer  of  these  shells  was 
observed  in  the  bank,  about  eighteen  inches  above  the  water  line  (the  water 
being  low),  in  a  position  that  indicated  the  old  bed  of  the  Salt  Fork  before 
the  canal  was  excavated.  High  water  would  wash  this  material  way  and 
provide  the  odd  valves  of  mussels  observed  in  different  parts  of  this  stream. 

Below  Maj^view  road  bridge  the  conditions  are  much  the  same  as  in 
the  neighborhood  of  the  Cottonwoods  bridge.  The  bottom  is  of  sand  and 
gravel,  with  some  mud  bordering  the  shore.  The  water  is  from  a  few 
inches  to  a  foot  in  depth,  the  channel  meandering  among  a  continuous 
series  of  sand  bars.  The  sand  is  ripple-marked  in  places  and  streaked 
with  bands  of  dark  green  algae,  with  yellowish  algae  in  spots.  The  surface 
of  the  flowing  portion  of  the  s^tream  is  thickly  covered  with  patches  of  dark 


84 


ILUNOIS  BIOLOGICAL  MONOGRAPHS 


[182 


green  putrescent  matter,  measuring  in  size  from  a  peanut  to  a  dish  pan. 
Some  of  these  masses  are  brownish,  where  the  algae  and  Protozoa  have  not 
completely  taken  possession  of  them. 

A  large  amount  of  oily  scum  may  be  observed  on  the  surface  and 
when  disturbed  the  bottom  emits  quantities  of  oily  matter,  as  is  the  case 
higher  up  the  stream.  On  exposed  bars  and  along  shore  the  algae  and 
putrescent  matter  have  dried  and  caked,  forming  a  pavement-like  layer. 
The  water  is  clearer  here  than  in  the  portion  of  the  stream  previously 
examined,  but  no  clean  water  life  could  be  found;  mussels,  crayfeh,  and 
insects  were  entirely  absent. 

Samples  of  the  bottom  from  the  stream  about  300  feet  east  of  the 
Mayview  road  bridge,  about  six  miles  below  the  Champaign  outlet  were 
examined.    The  following  life  was  present: 


Blue-green  algae 

Pediaslmm  simplex,  rare. 
PbortittdUtm  irtundalum,  common. 

Diat(»ns 
Nawicula  salinarum,  abundanL 
Praplaria  capudna,  abundant. 


Animals 

Ciliata,  minute,  abundant. 

Colpodium,  several. 

Euglena  genictdaia,  very  abimdant. 

Limnodrilus,  common. 

Nematode  worms,  minute,  abundant. 


About  a  mile  and  a  half  below  this  locality  additional  samples  were 
taken  for  examination.  Conditions  are  similar  but  the  water  is  not  as 
clear,  holding  more  sediment  in  suspension. 


Blue-green  algae 

Pedia^ntm  simplex,  rare. 
Pkormidiiim  immdatum,  abundant. 

Diatoms 
FragHaria  capucina,  abundant. 


Animals 

Ciliata,  minute,  abimdant. 
Paramoedum,  severaL 
Euglema  gemculata,  abundanL 
limnodrilus,  about  a  dozen. 
Nematode  worms,  minute,  many. 


At  the  last  north  and  south  farmer's  bridge,  the  canal  makes  a  wide 
sweep,  in  a  southeasterly  direction  (Fig.  43)  leaving  the  old  stream  bed 
to  the  west  of  the  new  channel,  in  the  form  of  an  *ox-bow'  almost  half 
a  mile  in  length,  which,  during  the  greater  part  of  the  year,  forms  a  large 
elongated  pond,  that  drains  into  Salt  Fork  canal  by  me^fos  of  a  small  outlet 
at  the  south  end  which  turns  abruptly  northeastward  as  it  empties  into  the 
canaL  At  the  time  examined,  the  bed  of  this  old  stream  was  almost  dry, 
following  a  period  of  very  dry  weather,  and  the  fauna  had  retired  to  several 
small,  shallow,  muddy  pools  which  remained  in  the  deeper  parts  of  the 
stream  bed.  An  examination  of  these  pools  disclosed  a  number  of  bull- 
heads (Ameiurus  melas)^  many  dragonfly  larvae  {Libellula  pulchdla)^ 
and  a  few  mollusks  {Planorbis  trivolvis,  Physa  gyrina,  and  Musculium 
transversum). 


183]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  85 

It  seems  evident  that  this  portion  of  the  old  stream  forms  a  reservoir 
from  which  certain  species  of  mollusks,  as  well  as  fish,  are  carried,  or  volun- 
tarily migrate,  through  the  outlet  into  Salt  Fork.  By  this  means  only 
can  the  presence  of  these  animals  in  the  polluted  water  be  accounted  for, 
because  none  have  been  seen  either  above  or  far  below  the  drain  from  the 
old  stream  channel.  The  specimens  of  Planorbis  trivolvis,  that  have  been 
observed  in  the  Salt  Fork  canal  below  the  east  and  west  road  bridge,  were 
probably  derived  from  this  source. 

Specimens  of  Planorbis  trivolvis  have  been  observed  in  the  Salt  Fork 
canal  which  probably  came  from  this  source.  Near  this  locality  a  school 
of  about  fifty  fingerling  bullheads  was  observed  on  May  29,  in  a  small 
part  of  the  stream  where  a  rather  deep  pool  had  developed.  They  were 
making  frantic  efforts  to  get  out  of  the  pool  but  the  surrounding  water 
was  too  shallow.  The  low  water  and  general  polluted  condition  of  the 
stream  evidently  provided  a  very  unfavorable  environment.  The  source 
from  which  these  fish  came  was  quite  likely  the  old  cut  off  portion  of  the 
original  Salt  Fork  from  which  place  they  had  been  carried  or  had  volun- 
tarily migrated,  when  the  water  was  higher  from  the  April  rains. 

From  the  east  and  west  road  bridge  (Fig.  45)  to  the  first  farmer's  bridge, 
a  distance  of  about  three-quarters  of  a  mile,  the  Conditions  are  the  same 
as  in  the  preceding  portion  of  the  canal.  The  water  is  clear  but  no  living 
mollusks  or  other  animals  could  be  found.  A  half  valve  of  Anodonta 
grandis,  badly  weathered,  and  a  few  bleached  valves  of  Sphaerium  solidu- 
lum,  were  the  only  evidences  of  molluscan  life.  These  had  evidently  been 
washed  from  the  old  stream  bed  at  some  point  where  it  was  exposed  by 
erosion  in  the  canal  walls.  The  same  algae  as  previously  observed  was 
floating  down  the  stream  in  large  green  patches.  Samples  of  these  green 
particles  were  examined  by  Professor  Smith  and  found  to  contain  such 
animals  as  Euglena  geniculata,  Paramoecium,  and  numerous  ciliate  Pro- 
tozoa, mostly  inhabitants  of  polluted  water. 

From  the  next  farmer's  bridge  to  the  eastward  turn  of  the  stream  the 
bottom  conditions  were  also  similar,  except  that  the  surface  of  the  water 
was  covered  with  an  oily  scum.  Groups  of  greater  or  less  size  of  gyrinid 
beetles  {Dineutes  assimilis)  were  seen  at  different  places  down  stream  for 
a  mile  or  more.  A  single  empty  shell  of  Planorbis  trivolvis  was  observed 
on  the  shore  of  the  west  bank  below  this  bridge.  No  living  clams  were 
seen,  nor  any  mutilated  valves. 

From  the  eastward  turn  of  the  stream  to  the  mouth  of  Spoon  River, 
the  canal  is  in  bad  condition,  the  water  being  dirty  and  oily,  with  numer- 
ous bubbles  of  gas  rising  constantly  from  the  bottom,  which  also  gave  off 
quantities  of  oily  scum  when  disturbed  (Fig.  44).  The  water  is  shallow 
and  conditions  as  already  described  for  the  stream  higher  up.     Green 


86 


ILUNOIS  BIOLOGICAL  MONOGRAPHS 


[184 


putrescent  matter  is  not  quite  as  abundant  as  higher  up  in  the  canal 
and  the  odor  is  not  as  bad. 

Samples  were  collected  from  a  point  about  a  mile  above  the  junction 
of  Salt  Fork  with  the  Spoon  River.  Organisms  were  fewer  in  both  species 
and  individuals. 


Blue-green  algae 

Phormidium  inundaium,  common. 

Diatoms 
Synedea  pulchella,  abundant. 
Fragilaria  capucina,  abundant. 


Animals 

Ciliata,  abundant. 
Euglena  geniculala. 
Limnodrilus,  a  few  individuals. 


Below  the  mouth  of  Spoon  River  conditions  are  also  bad.  Where  the 
current  is  strong,  sand  bars  have  been  formed  which  cover  the  black  mud 
beneath.  Everywhere,  except  in  the  channel  where  it  is  sandy,  the  bottom 
is  of  soft  mud,  eight  to  fifteen  inches  deep,  filled  with  ill-smelling  gasses. 
Sewage  conditions  here  are  bad,  the  water  having  a  foul  smell.  When 
wading  in  the  water,  the  disturbed  mud,  which  is  black  and  oozy,  con- 
stantly gives  off  bubbles  of  gasses  that  rise  to  the  surface  and  break.  This 
condition  is  uniform  for  the  entire  stretch  of  stream  bed  examined,  about 
a  third  of  a  mile,  from  near  the  mouth  of  Spoon  River  to  the  middle  of  the 
big  bend  above  St.  Joseph.  The  surface  of  the  water  is  usually  covered 
with  a  film  of  oil  resembling  petroleum. 

No  living  mussels  could  be  found  in  this  area.  A  single  valve  of  Am- 
hlema  undulata  was  seen  near  the  mouth  of  Spoon  River  which  was  prob- 
ably brought  to  its  resting  place  from  Spoon  River  during  a  period  of 
flood.  It  is  noteworthy  that  while  no  mussels  or  gill-bearing  snails  were 
observed  in  this  part  of  Salt  Fork,  several  species  of  fresh  water  pul- 
monates  were  seen  in  considerable  numbers,  indicating  that  here,  as 
elsewhere,  the  pulmonates  are  able  to  live  in  water  which  is  totally 
lyifit  for  mussels  and  gill-bearing  moUusks. 

Examples  of  the  bottom  sediments  and  green  masses  floating  in  the 
water  were  taken  from  the  stream  about  a  hundred  feet  below  the  mouth 
of  Spoon  River.  Algae  was  plentiful  and  included  Phormidium  inundaium, 
a  blue-green  species,  in  abundance.  Two  species  of  diatoms,  Navicula 
salinarum  and  Fragilaria  capucina,  were  also  present.  Of  animals,  Limno- 
drilus was  well  represented,  but  Euglena  geniculala  was  not  common,  and 
ciliate  Protozoa  were  much  less  numerous  than  in  samples  taken  from 
stations  higher  up  in  the  stream.  Salt  Fork  here  shows  the  influence  of 
the  added  cleaner  water  from  Spoon  River. 

At  the  mouth  of  Spoon  River  a  bar  has  been  formed,  by  natural  or 
artificial  agencies,  which,  except  for  a  space  about  four  feet  wide,  holds 
back  the  waters  of  that  stream  (Fig.  16).  An  examination  was  made 
of  Spoon  River  about  400  feet  above  this  bar.    Here  five  species  of  mussels 


185]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  87 

were  found,  in  more  or  less  abundance,  and  insects  were  also  abundant. 
The  water  is  low,  two  or  three  feet  deep  in  the  channel  in  the  fall  and  the 
bottom  is  very  muddy.  A  very  small  amount  of  green  algae  was  noted 
on  the  surface,  evidently  brought  up  from  Salt  Fork.  The  mussels  col- 
lected included: 

Lasmigona  complanata  Lampsilis  luteola 

Amblema  undulata  Eurynia  lienosa 

Carunculina  parva 

A  water  boatman  (Corixa,  near  burmeisteri)  was  very  abundant, 
especially  in  the  nymph  stage,  as  were  also  numerous  gyrinid  beetles 
(Dineutes  assimilis).  Though  the  water  was  low,  men  were  observed 
fishing  for  bullheads  in  this  part  of  Spoon  River.  The  contrast  between 
this  stream,  with  its  abundance  of  clean  water  life,  and  the  adjacent  parts 
of  Salt  Fork,  which  is  utterly  devoid  of  clean  water  life,  strikingly  indicates 
the  harmful  effects  of  sewage  pollution  on  the  fauna  of  our  streams. 

Samples  of  the  green  matter  floating  on  the  water  of  the  Spoon  River 
were  examined  and  found  to  contain  Euglena  geniculata,  common,  ciliate 
Protozoa,  many.  These  masses  seem  to  be  made  up  almost  entirely  of 
these  animals  and  low  plants,  of  which  three  species  were  noted:  Phormi- 
dium  inundatum  alga;  Navicula  salinarum  and  Fragilaria  capucina,  dia- 
toms.   A  single  pupa  of  Chironomus  decorus  was  found  at  this  place. 

For  a  distance  of  several  miles  below  St.  Joseph  unfavorable  conditions 
seem  to  prevail,  no  living  mussels  being  found  for  a  distance  of  over  four 
miles,  and  here  they  occur  rarely.  Living  mussels  are  not  found  in  any 
number  for  a  distance  of  over  five  miles  below  St.  Joseph.  These  animals 
are  not  abundant  in  species  and  individuals  until  a  distance  of  twenty  miles 
has  been  traversed  below  Urbana.  Conditions  for  a  distance  of  two  miles 
below  St.  Joseph  are  similar  to  those  described  for  the  area  just  below 
Spoon  River,  the  bottom  consisting  of  black  mud  from  which  bubbles  of 
ill-smelling  gas  rise  when  the  bottom  is  disturbed.  Below  this  point  condi- 
tions begin  to  improve,  though  very  gradually. 

That  conditions  along  the  polluted  portion  of  Salt  Fork  are  often,  if  not 
always,  highly  objectionable  was  evidenced  from  conversations  with  far- 
mers living  near  the  stream.  One  farmer,  who  had  built  a  small  house 
within  a  few  hundred  feet  of  the  stream,  stated  that  the  "stench  was  at 
times  almost  unbearable"  and  that  people  living  half  a  mile  away  were 
strongly  conscious  of  the  odor.  This  was  about  five  miles  down  the 
stream  from  Urbana.  A  gentleman  driving  along  the  road  which  parallels 
the  Salt  Fork  east  of  Cottonwoods  road,  stated  that  the  odor  on  Septem- 
ber 10  was  very  obnoxious.  People  living  a  mile  south  and  north  of  the 
stream  do  not  suffer  from  these  odors. 


88  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [186 

SUMMARY    or    SALT   FORK    CONDITIONS 

It  has  been  shown  in  the  previous  pages  that  the  sewage  and  other 
wastes  that  drain  into  the  Salt  Fork  from  the  Twin  Cities  have  driven  out 
or  killed  all  clean  water  life  from  the  junction  of  the  Boneyard  with  Salt 
Fork  to  a  point  about  four  miles  below  St.  Joseph,  or  fourteen  miles  below 
Urbana.  At  this  point  a  few  living  mussels  are  found  and  also  a  few  cray- 
fish. One  must  pass  down  the  stream  for  a  distance  of  twenty  miles  before 
encountering  a  normal  river  fauna,  comparable  to  that  found  in  Spoon 
River  at  a  point  less  than  a  mile  above  the  junction  of  that  stream  with 
Salt  Fork.  The  abundance  of  clean-water  life  in  Spoon  River  is  in  marked 
contrast  with  the  total  absence  of  this  kind  of  life  in  Salt  Fork,  which 
normally  would  have,  in  suitable  habitats,  a  similar  fauna  in  the  barren 
stretch  of  ten  miles  between  the  two  localities  compared.  No  better 
example  is  known  of  the  total  annihilation  of  a  fauna  from  so  great  a  dis- 
tance as  the  result  of  polluted  conditions. 

Foul  water  algae  and  Protozoa,  as  well  as  some  other  animal  life  (slime 
worms)  characteristic  of  polluted  water,  are  abundant  in  that  portion  of 
the  stream  devoid  of  clean  water  life.  The  same  relative  conditions  were 
observed  by  Forbes  and  Richardson  in  their  study  of  the  Illinois  River. 

Fish,  especially  young  fish,  have  been  made  an  index  to  the  degree  of 
pollution  of  streams.  It  would  seem  from  observations  made  during  the 
course  of  the  present  study,  as  well  as  from  other  occasions  and  in  other 
places,  that  bottom-inhabiting  animals,  such  as  river  mussels  and  cray- 
fish, provide  a  better  index  for  this  purpose.  Fish  are  able  to  migrate 
easily  and  swiftly  from  an  unfavorable  to  a  more  favorable  environment, 
but  these  more  sedentary  animals,  especially  the  mussels,  cannot  change 
their  eiivironment  so  easily  and  must  either  adapt  themselves  to  the  more 
unfavorable  conditions  or  perish.  For  example,  young  bullheads  were 
observed  in  Salt  Fork  about  three  miles  above  St.  Joseph  in  the  spring 
when  the  water  was  comparatively  high.  But  no  mussels  or  crayfish 
have  been  seen  within  five  miles  of  this  point.  This  indicates  clearly 
that  fish  are  more  flexible  in  this  matter  than  the  mussels  and  crayfish, 
which  are  not  as  mobile.  Ortmann  (1909:93-94)  believes  that  crayfish  are 
slightly  more  resistant  than  mussels  to  polluted  conditions,  and  as  scaven- 
gers (they  have  been  observed  eating  dead  mussels)  they  could  naturally 
withstand  a  limited  degree  of  unfavorable  environment.  Observations 
made  on  the  Salt  Fork,  however,  indicate  that  the  two  groups  appear  at 
about  the  same  time. 

Forbes  and  Richardson  (1913:498)  distinguish  three  stages  of  impurity 
of  streams,  which  may  apply  equally  well  to  either  the  stream  itself  or  to 
the  organisms  living  in  the  stream.  These  terms  are  "given  in  the  order 
of  diminishing  impurity,  namely,  (1)  septic  or  saprobic,  (2)  polluted  or 


187  ]  FA  UNA  OF  BIG  VERMJUON  RIVER— BAKER  89 

pollutional,  and  (3)  contaminated  or  contaminate;  and  to  these  we  will 
add  'clean-water'  to  indicate  the  conditions  and  organisms  substantially 
equivalent  to  those  of  the  natural,  uncontaminated  stream." 

Judging  Salt  Fork  by  these  standards  of  impurity,  we  would  say  that 
from  the  Urbana  sewage  outlet  to  the  first  bridge  below  the  Champaign 
sewer  outlet,  a  distance  of  about  two  miles,  the  stream  is  in  a  septic  condi- 
tion. From  this  point  to  about  two  miles  below  St.  Joseph  it  is  polluted. 
From  this  region  to  Homer  Park,  below  the  dam,  it  is  contaminated. 
Below  the  dam  there  is  probably  some  contamination  at  times,  but  the 
fauna  is  a  clean  water  one  and  the  stream  would  be  classed  as  a  clean  water 
stream,  being  unmodified  by  sewage  conditions.  The  lower  part  of  Salt 
Fork  near  Middle  Fork,  and  Middle  Fork  and  the  Big  Vermilion  as  far  as 
Danville  are  clean- water  streams  with  a  large  and  varied  fauna  of  mussels, 
crayfish,  and  insect  larvae.  Below  Danville  there  is  sewage  pollution,  and 
conditions  are  again  unfavorable. 


90  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [188 


SUMMARY  AND  CONCLUSIONS 

The  mussel  fauna  of  the  Big  Vermilion  River  consists  of  at  least  35 
species  and  varieties.  Ten  species  of  small  pelecypods  and  15  species 
of  gastropods  also  occur,  making  a  total  molluscan  fauna  of  60  species 
and  varieties  occurring  in  a  distance  of  upwards  of  50  miles.  The  mussel 
fauna  of  this  stream  compares  well  with  that  of  two  other  Illinois  streams 
of  comparable  size,  the  Sangamon,  150  miles  long,  with  25  species,  and  the 
Kankakee,  300  miles  long,  with  48  species.  The  total  length  of  the  Big 
Vermilion  River  is  90  miles,  with  35  species.  Seventeen  species  of  Naiades 
occur  in  the  Big  Vermilion  River  that  have  not  been  found  in  the  Sangamon 
River,  while  five  species  have  been  collected  from  the  Sangamon  that  have 
not  yet  been  detected  in  the  Big  Vermilion.  The  former  stream  belongs 
to  the  Mississippi  drainage  while  the  latter  is  a  part  of  the  Wabash  drain- 
age. 

In  the  Big  Vermilion  it  was  noted  that  there  was  a  progressive  increase 
in  number  of  species  as  the  distance  down  stream  increased,  the  head- 
waters containing  but  few  species,  which  are  usually  smaller  than  the 
same  species  from  lower  down  in  the  stream.  It  was  also  observed  that 
the  headwater  inhabitants,  as  well  as  many  naiads  farther  down  the  stream, 
were  more  compressed  and  of  greater  comparative  length  than  the  same 
species  as  it  occurred  in  the  larger  part  of  the  river. 

The  dam  at  Homer  Park,  27  miles  below  Urbana,  appears  to  form  a 
barrier  between  the  fauna  above  and  below  this  obstruction.  Above  the 
dam,  19  species  occur,  while  below  the  dam,  ^2>  species  have  been  observed. 
It  is  noteworthy  that  immediately  above  the  dam  the  largest  number  of 
species  found  at  one  habitat  was  14,  while  below  the  dam,  at  Homer 
Park,  28  species  have  been  collected.  It  is  probable  that  the  fall  of  water 
over  the  dam  aerates  the  stream  and  provides  an  especially  favorable 
environment  for  the  mussels. 

UNFAVORABLE    INFLUENCES 

Sewage  pollution  has  killed  all  clean  water  life  for  a  distance  of  fourteen 
miles  below  Urbana  and  has  made  the  stream  an  unfavorable  environ- 
ment for  a  distance  of  twenty  miles.  Below  this  point  the  fauna  is  normal 
and  is  not  affected  by  sewage  conditions.  In  the  desert  area  between  St. 
Joseph  and  Urbana,  slime  worms  and  septic  Protozoa  were  observed 
among  the  animals  and  foul  water  algae  among  the  plants.  A  few  beetles, 
breathing  free  air,  were  observed  in  the  stream  near  St.  Joseph  and  for 
some  distance  above  this  locality.    Many  of  the  old  pond-like  bodies  of 


189]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  M 

water  left  on  either  side  of  the  new  drainage  ditch  are  inhabited  by 
clean  water  animals  that  occasionally  get  into  the  ditch  during  periods 
of  high  water.  Fish,  moUusks,  and  insects  have  been  observed  which 
doubtless  came  from  this  source. 

PARASITES  AND  PATHOLOGIC  AGENCIES 

As  a  rule,  parasites,  either  distomids  or  Unionicola  (Atax)  were  rare 
in  the  naiads  collected  in  the  Big  Vermilion  and  Sangamon  rivers.  Some 
of  the  Anodontas  had  marginal  cists  of  distomids  and  many  shells  of  this 
genus  were  discolored  from  this  cause.  Clark  and  Wilson  (1912:61),  in 
their  study  of  the  Maumee  River  fauna,  observed  distomids  in  various 
mussels  which  were  believed  to  be  the  distomids  described  by  Osborn  and 
Kelly.  The  affected  mussels  were  Actinonaias  Ugamentina,  Obovaria 
cir cuius,  EUiptio  gibbosus,  Lampsilis  ventricosa,  Amblema  undulata,  Las- 
migona  costata  (thought  to  be  the  distomid  of  Kelly),  and  Anodonta 
grandis  (thought  to  be  the  distomid  of  Osborn).  It  is  probable  that  these 
flat-worms  also  infest  many  of  the  mussels  of  the  rivers  investigated,  but 
they  were  not  observed  in  the  specimens  collected.  Cotylaspis  insignis 
and  forms  of  Unionicola  were  also  found  by  Clark  and  Wilson,  but  these 
parasites  were  not  seen  in  the  mussels  examined  from  the  area  under  con- 
sideration. 

Pearls,  usually  of  small  size,  were  frequently  seen  attached  to  the 
shells  of  mussels,  and  many  pearly  growths  cause  by  injuries  were  also 
observed.  A  large  round  pearl  was  found  in  a  shell  of  Anodonta  grandis 
gigantea  from  Crystal  Lake,  which  measured  almost  a  quarter  of  an  inch 
in  diameter  (5  mm.).  It  has  been  suggested  that  many  of  these  pearls  and 
pearly  growths  attached  to  the  mussels  may  have  been  caused  by  parasites, 
such  as  the  distomids  before  mentioned.  The  same  is  also  true  of  the  round 
pearls  found  in  the  animal  tissues  of  the  mussels. 

Crippled  shells,  those  individuals  have  abnormal  valves,  were  not  com- 
mon in  either  of  the  rivers  examined.  Mud  was  found  to  cause  trouble  in 
many  cases,  getting  in  between  the  mantle  and  the  shell  below  the  pallial 
line  and  causing  large  blisters. 

ECONOMIC  CONSIDERATIONS 

The  shells  known  as  river  mussels  or  Naiades  are  used  in  the  manufac- 
ture of  pearl  buttons.  As  this  industry,  the  making  of  pearl  buttons,  has 
reached  large  proportions  it  is  imperative  that  the  raw  material  be  con- 
served for  the  maintenance  of  the  industry.  The  continued  fishing  of  the 
mussel  beds  in  the  larger  rivers  has  greatly  depleted  the  amount  of  avail- 
able raw  material — the  mussel  beds — ,  and  the  whole  industry,  shell  collect- 
ing and  button  making,  is  threatened  with  disaster  if  means  are  not  found  to 
restock  the  depleted  beds  (see  Coker,  1919:44).  The  United  States  Bureau 


92  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [190 

of  Fisheries  has  conducted  many  interesting  experiments  on  the  propaga- 
tion of  mussels  by  the  artificial  infection  of  fish  with  mussel  glochidia  and 
the  means  and  methods  for  restocking  these  cleaned-out  areas  are  at  hand. 
It  only  remains  for  proper  laws  to  be  passed  and  enforced,  by  the  states  or 
federal  government,  or  both,  regulating  the  time  and  place  in  which  shelling 
operations  may  be  carried  on.  Reasonable  time  must  be  given,  at  least 
three  years,  for  the  recovery  of  a  depleted  mussel  bed. 

In  this  connection  it  would  seem  that  the  mussel  fauna  of  such  a  stream 
as  the  Big  Vermilion  River  might  form  a  reservoir  from  which  the  depleted 
beds  farther  down  the  stream  might  be  restocked  by  fish  which  had  been 
infected  with  glochidia  from  the  commercial  species  living  in  the  smaller 
stream.  The  Big  Vermilion  contains  eleven  species  that  are  used  for 
cutting  button  blanks  and  are  considered  valuable  for  this  purpose  by  the 
button  manufacturers.    These  are: 

Amblema  undtdata    Blue  point 
Lampsilis  luteola    Fat  mucket 
Latnpsilis  anodontoides    Yellow  sand-shell 
Lampsilis  ventricosa    Pocket-book 
Tritogonia  tuberculata    Buckhom 
Quadrtda  puslulosa    Warty-back 
Quadrtda  lachrymosa    Maple-leaf 
Actinonaias  ligamentina    Mucket 
Fusconaia  rubiginoas    "Wabash  pig-toe 
Lasmigona  complanata    White  heel-splitter 
Lasmigona  costata    Fluted  shell 

Several  of  the  smaller  shells  are  also  used  when  shells  are  scarce,  as 
Lampsilis  compressa,  Quadrula  metanevra,  Ohovaria  circulus,  and  Strophitus 
edentulus.  In  the  Sangamon  River  about  the  same  number  of  species  suit- 
able for  the  button  industry  occur  and  these  are  usually  of  fine  quality. 

In  their  survey  of  the  mussel  fauna  of  the  Kankakee  basin,  Wilson  and 
Clark  (1912:35)  recognize  the  value  of  these  smaller  streams,  with  a  fauna 
too  small  in  individuals  to  be  used  by  the  shell  fishermen,  but  containing 
many  of  the  essential  species  from  which  good  button  blanks  may  be  cut. 
These  authors  say:  "The  most  valuable  species  are  all  good  breeders 
throughout  the  basin.  This,  taken  in  connection  with  the  excellent  quality 
of  the  shells  they  produce  and  the  good  railroad  facilities  everywhere 
available,  makes  this  basin  one  of  the  best  yet  examined  for  the  supply 
of  glochidia  to  be  used  in  artificial  mussel  propagation."  This  statement 
might  apply  with  almost  equal  force  to  the  Big  Vermilion,  which  may 
sometime  be  needed  for  a  reservoir  from  which  to  propagate  the  mussels 
in  the  larger  rivers. 

Whether  all  of  the  fishes  which  have  proved  the  most  satisfactory  hosts 
for  glochidia  are  abundant  here  is  not  known,  but  as  young  of  nearly  all  the 


191]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  93 

commercial  shells  were  observed,  it  follows  that  the  fishes  carrying  the 
glochidia  must  also  be  present. 

The  Big  Vermilion  River  is  seen,  therefore,  to  be  a  valuable  asset  to  the 
State,  containing  a  fauna  of  both  biologic  and  economic  importance, 
which  should  be  conserved  for  possible  use  as  a  restocking  reservoir  for 
the  larger  rivers.  Pollution  should  be  reduced  to  a  minimum  and  the 
timber  along  the  banks,  especially  of  the  headwaters,  should  be  conserved 
in  order  that  the  water  may  be  held  in  the  ground  and  gradually  flow  into 
the  streams,  instead  of  running  off  in  floods,  causing  excessive  high  water 
in  the  spring  and  extremely  low  water  in  the  fall  and  winter.  It  would  be 
possible  to  reforest  many  parts  of  the  upper  branches  of  the  streams, 
where  they  are  low  or  irregular  places  unfit  for  farming  operations. 


94  JLUNOIS  BIOLOGICAL  MONOGRAPHS  [192 


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Fish.,  28:615-626. 


193]  FA  UNA  OF  BIG  VERMILION  RIVER— BAKER  95 

1910.    Reproduction  and  Parasitism  in  the  Unionidae.    Joum.  Exper.  Zool.,  9:79-115, 
pi.    1-5. 
Leighton,  Marshall  O. 

1904.    Quality  of  Water  in  the  Susquehanna  River  Drainage  Basin.  Water  Supply  and 
Irrigation  Paper  No.  108,  U.  S.  Geol.  Surv.,  76  pp. 
Leverett,  Frank. 

1899.    The  Illinois  Glacial  Lobe.     U.  S.  Geol.  Surv.  Mon.  38. 
Marsh,  M.  C. 

1908.  Notes  on  the  Dissolved  Content  of  Water  in  its  Effect  upon  Fishes.    Bull.  Bur. 

Fish.,  28:891-906. 
Ortmann,  a.  E. 

1909.  The  Destruction  of  the  Fresh-water  Fauna  in  Western  Pennsylvania.     Proc. 

Amer.  Phil.  Soc.,  48:90-110,  1  pi. 
1912.    Notes  on  the  Families  and  Genera  of  the  Najades.    Ann.  Carnegie  Mus.,  8:222- 

365. 
1918.    The  Nayades  (Fresh-water  Mussels)  of  the  Upper  Tennessee  Drainage,  with  Notes 

on  S)Tionymy  and  Distribution.    Proc.  Amer.  Phil.  Soc,  57:521-626. 
1920.     Correlation  of  Shape  and  Station  in  Fresh-water  Mussels  (Naiades).   Proc.  Am. 

PhU.  Soc,  59:  pp.  267-312. 
1920a.  A  Monograph  of  the  Naiades  of  Pennsylvania.    Part  III.    Systematic  Accoimt  of 

the  Genera  and  Species.    Mem.  Carnegie  Mus.,  8:1-384,  21  pi. 
Pennsylvania. 

1918,    Industrial  Waste  Survey  of  the  Clarion  River  Basin.     Ann.  Rept.  Commis, 

Health,  Penn.,  10:1279-1316. 
Shelford,  V.  E. 

1917.  An  Experimental  Study  of  the  Effects  of  Gas  Waste  upon  Fishes,  with  Especial 

Reference  to  Stream  Pollution.    Bull.  State  Lab.  Nat.  Hist.,  11:378-425. 

1918.  Ways  and  Means  of  Measuring  the  Dangers  of  Pollution  to  Fisheries.    Bull.  111. 

Nat.  Hist.  Surv.,  13:23-42. 
Simpson,  C.  T. 

1914.  A  Descriptive  Catalogue  of  the  Naiades,  or  Pearly  Fresh-Water  Mussels.   Bryant 

Walker,  Detroit,  Mich.    1540  pp. 
Smith,  Frank. 

1915.  Two  New  Varieties  of  Earthworms  with  a  Key  to  Described  Species  in  Illinois. 

Bull.  State  Lab.  Nat.  Hist.  10:551-559,  1  pi. 

SURBER,  ThADDEUS. 

1912.  Identification  of  the  Glochidia  of  Fresh-water  Mussels.    Bur.  Fish.  Doc,  771, 

10  pp.  3,  pi. 

1913.  Notes  on  the  Natural  Hosts  of  Fresh-water  Mussels.     Bull.  Bur.  Fish.,  32: 

101-116,  3  pi. 

1915.  Identification  of  the  Glochidia  of  Fresh-water  Mussels.    Bur.  Fish.  Doc,  813,9 

pp.  1  pi. 
Utterbach,  W.  I. 

1916.  The  Naiades  of  Missouri.    Amer.  Midland  Nat.,  4,  nos.  1-10,  200  pp.,  29  pi. 
1916.    Breeding  Record  of  Missouri  Mussels.   Privately  printed,  8  pp. 

Walker,  Bryant. 

1918.    A  Synopsis  of  the  Classification  of  the  Fresh-water  Mollusca  of  North  America 
north  of  Mexico,  and  a  Catalogue  of  the  More  Recently  Described  Species, 
with  Notes.     Univ.  Mich.,  Mus.  Zool.,  Misc.  Publ.,  no.  6.  213  pp.,  many  cuts. 
Ward,  H.  B. 

1918.    The  Elimination  of  Stream  Pollution  in  New  York  State.    Trans.  Amer.  Fish. 
Soc,  48:25  pp. 


96  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [194 

1919.     Stream  Pollution.      Jour,  Amer.  Water  Works  Assoc.,  6:823-831. 

1919.  Stream  Pollution  in  New  York  State.    A  Preliminary  Investigation  of  the  Prob- 

lem from  the  Standpoint  of  the  Biologist.    New  York  Conserv.  Comm.,  79  pp., 

3  pi. 
Wells,  M. 

1918.    The  Reactions  and  Resistance  of  Fishes  to  Carbon  Dioxide  and  Carbon  Monoxide. 

BuU.  III.  State  Lab.  Nat.  Hist.,  11:557-571. 
Wells,  W.  F. 

1920.  Conservation  of  the  Quality  of  Water  of  New  York  State  as  a  Natural  Resource. 

Science,  52:279-284. 
Wilson,  C.  B.  and  Clark,  H.  W. 

1912.    The  Mussel  Fauna  of  the  Kankakee  Basin.    Bur.  Fish,  Doc,  758,  52  pp.,  pi.  and 

map. 
1914,    The  Mussels  of  the  Cumberland  River  and  its  Tributaries.    Bur.  Fish.  Doc,  781, 
63  pp.,  1  pi. 


195]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  97 


PLATE  I 


96  ILUNOJS  BIOLOGICAL  MONOGRAPHS  (196 


EXPLANATION  OF  PLATE 

Fig.  1.   Drainage  ditch  above  Urbana,  east  of  cemetery.   Station  2. 

Fig.  2.  Salt  Fork  south  of  Muncie.  Note  water  willow  in  center  of  stream  bed;  also 
niunerous  bare  portions  of  stream  bed,  the  river  appearing  as  a  series  of  pools.  October,  1919. 
Station  26. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


^^^^^E^^Sf>^'9^^r'^ 

MHBHH 

■ 

MHHI| 

■■ 

^^■|/^''     '^:^ 

^HH| 

^ 

^^^B          "^ 

* 

^^K    % 

jHi 

ii 

^ 

BAKER 


FAUNA  OF  BIG  VERMILION  RIVER  PLATE  I 


197]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  99 


PLATE  II 


100  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [198 


EXPLANATION  OF  PLATE 

Fig.  3.  Old  stream  bed  of  Salt  Fork  in  Busey  woods,  north  of  Crystal  Lake,  Urbana. 
Original  habitat  for  Planorbis  pseudotrivolvis .    Station  3. 

Fig.  4.  Junction  of  Middle  Fork  with  Salt  Fork  to  form  the  Big  Vermilion  River.  Look- 
ing south  from  road  bridge  crossing  Middle  Fork.    September  26, 1920. 

Fig.  5.  Middle  Fork  a  fourth  of  a  mile  above  junction  with  Salt  Fork.  Bed  of  river 
exposed  in  foreground.   Station  29.    September  26, 1920. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER  FAUNA  OF  BIG  VERMILION  RIVER  PLATE  II 


199]  FA  UNA  OF  BIG  VERMIUON  RI VER— BAKER  101 


PLATE  III 


102  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [200 


EXPLANATION  OF  PLATE 

Fig.  6.    Spoon  River,  seven-tenths  of  a  mile  above  Salt  Fork.   Station  10.    September 
28,  1918. 

Fio.  7.    Spoon  River,  riflBes  below  bridge,  same  locality  as  Fig.  6. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER 


FAUNA  OF  BIG  VERMILION  RIVER        PLATE  III 


2011  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  103 


PLATE  IV 


104  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [202 


EXPLANATION  OF  PLATE 

Fig.  8.    Bench  mark  655,  Salt  Fork,  above  road  bridge.  Station  17.  September  13, 1918. 
Fig.  9.    Salt  Fork  two  and  a  half  miles  north  of  Sidney,  looking  north,  the  Champaign 
moraine  on  the  left,  a  flood  plain  on  the  right.   Station  18.   September  13, 1918. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


^J^■4*..                               lis 

ni 

^^^^^^^^^^^^^H^^^^^Dt  flBr^^^l^^^^^BII 

§m 

BAKER  FAUNA  OF  BIG  VERMILION  RIVER         PLATE  IV 


203]  FA  UNA  OF  BIG  VERMIUON  RIVER— BAKER  105 


PLATE  V 


106  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [204 


EXPLANATION  OF  PLATE 

Fig.  10.    Iron  bridge  one  mile  north  of  Sidney.   Station  19.  August  26, 1918. 
Fig.  11.    Cement  bridge  northeast  of  Sidney.    Note  large  area  of  water  lily,  Nym- 
pkaea  advena.    Station  20,  August  26,  1918. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER 


FAUNA  OF  BIG  VERMILION  RIVER  PLATE  V 


20S]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  107 


PLATE  VI 


108  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [206 


EXPLANATION  OF  PLATE 

Fig.  12.  Salt  Fork  three  and  a  half  miles  above  Homer  Park,  Station  23.  October  4, 
1918. 

FiG.  13.  Salt  Fork.  Deep  pool  below  dam  and  rapids.  Professor  Smith's  field  laboratory 
during  a  period  of  twenty  years.    Station  25.    November  4,  1920. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER  FAUNA  OF  BIG  VERMILION  RIVER         PLATE  VI 


207]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  109 


PLATE  VII 


110  ILLINOIS  BIOLOGICAL  MONOGRAPES  [208 


EXPLANATION  OF  PLATE 

Fig.  14.  Dam  in  Salt  Fork  at  Homer  Park.  The  dam  is  just  below  the  interurban 
bridge  and  is  five  feet  high.    November  4,  1920. 

Fig.  15.  Salt  Fork  below  dam  at  Homer  Park.  Shallow  water  and  rocky  bottom.  No- 
vember 4, 1920.    Part  of  Station  25. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER  FAUNA  OF  BIG  VERMILION  RIVER        PLATE  VII 


209]  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  111 


PLATE  VIII 


112  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [210 


EXPLANATION  OF  PLATE 

Fig.  16.  Salt  Fork  and  mouth  of  Spoon  River.  Rowboat  marks  outlet  of  Spoon  River 
through  bar.    September  24,  1920. 

Fig.  17.  Valley  of  Big  Vermilion  River  from  crest  of  bank  at  Gray's  Siding.  October  8, 
1920. 

Fig.  18.  Cutting  through  shale  rock  covered  with  glacial  deposits.  Big  Vermilion  River 
one  mile  below  mouth  of  Middle  Fork.   Station  30.   October  8, 1920. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER 


FAUNA  OF  BIG  VERMILION  RIVER      PLATE  VIII 


211]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER.]  113 


PLATE  IX 


114  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [212 


EXPLANATION  OF  PLATE 

Fig.  19.  Rock  bed  of  Big  Vermilion  River  one  mile  below  Middle  Fork.  Station  30. 
October  8,  1920. 

Fig.  20.  Sandbar  in  center  of  riverbed,  several  himdred  feet  below  fig.  1.  Station  30. 
Octobers,  1920. 

Fig.  21.  Junction  of  Boneyard  with  Salt  Fork.  Boneyard  on  right  above  ice.  December 
20, 1919. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER  FAUNA  OF  BIG  VERMILION  RIVER        PLATE  IX 


213]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  11^ 


PLATE  X 


116 


ILUNOIS  BIOLOGICAL  MONOGRAPHS 


[214 


EXPLANATION  OF  PLATE 


Fig.  22.  Anodonla  grandis. 
Fig.  23.  Anodonta  grandis. 
Fig.  24.  Anodonta  grandis. 
Fig.  25.  Amblemaundulaia. 
Fig.  26.  Amblema  undulaia. 
Fig.  27.  Amblema  undtdata. 
Fig.  28.  Amblema  undtdata. 
margin  of  shell. 


Right  valve  with  pearly  growths  at  anterior  end. 

Left  valve  with  injured  portion  folded  inward. 

Pearly  formation  in  left  valve. 

Right  valve  uninjured. 

Left  valve  with  large  blister  inside  pallial  line. 

Left  valve  with  abnormal  pallial  line. 

Left  valve  with  pin-head  pearls  between  pallial  line  and 


Pathologic  musseb  from  Salt  Fork. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


24 


26 


BAKER  FAUNA  OF  BIG  VERMILION  RIVER  PLATE  X 


215J  FAUNA  OF  BIG  VERMIUON  RIVER— BAKER  117 


PLATE  XI 


118  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [216 


EXPLANATION  OF  PLATE 

Fig.  29.  Amblema  undulaia.   Left  valve  with  channel  due  to  injury. 

Fig.  30.  Amblema  undidata.  Right  valve  with  ridge  due  to  same  injury. 

Fig.  31.  Strophitus  edentidus.  Right  valve  with  pearl  near  posterior  end. 

Fig.  32.  Strophitus  edentidus.    Left  valve  with  distomid  discoloration. 

Fig.  33.  Lasmigona  costata.    Right  valve  with  repaired  injury  near  posterior  end. 

Fig.  34.  Amblema  undulata.    Spoon  River  form  with  rounded  shell. 

Fig.  35.  Lampsilis  ventricosa.    Left  valve  with  injured  postero-ventral  margin. 

Pathologic  mussels  from  Salt  Fork. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER  FAUNA  OF  BIG  VERMILION  RIVER         PLATE  XI 


217J  FA  UNA  OF  BIG  VERMIUON  RI VER— BAKER  119 


PLATE  XII 


120  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [218 


EXPLANATION  OF  PLATE 

Fig.  36.  Junction  of  Boneyard  with  Salt  Fork  canal,  looking  west  Note  high  bank  on 
left  where  mussel  shells  were  found,  indicating  bottom  of  bed  of  Salt  Fork  stream  before  the 
canal  was  dug.    Sludge  bank  in  foregroimd.    September  14,  1920. 

Fig.  37.  Salt  Fork  canal  three-fourths  of  a  mile  below  first  iron  bridge  east  of  Urbana. 
December  31, 1919. 

Fig.  38.  Farmer's  bridge  across  Salt  Fork  canal,  one-half  mile  below  Brownfield  W*ods 
bridge.   December  31, 1919. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


iMm, 

mJf^li^ 

1^1 

57 

wmk-  .'.-..^^'        ^it^^^E'ia^HHHH 

BAKER  FAUNA  OF  BIG  VERMILION  RIVER       PLATE  XII 


219]  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  121 


PLATE  XIII 


122  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [220 


EXPLANATION  OF  PLATE 

Fig.  39.  Boneyard  just  below  Urbana  septic  tank  outlet.    September  14,  1920. 

Fig.  40.  Salt  Fork  canal  west  of  Cottonwood's  road  bridge.  Note  bare  sand  bars  with 
stream  meandering  between.  Bars  are  covered  with  green  putrescent  matter  dried  by  the 
sun.  September  14,  1920. 

Fig.  41.  Salt  Fork  canal  at  entrance  of  small  ditch  from  Champaign  outfall  pipe.  Note 
sludge  bank  in  foreground  and  sewage  indicated  by  daxk  color  of  water  in  center  of  picture. 
September  14, 1920. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER 


FAUNA  OF  BIG  VERMILION  RIVER     PLATE  XIII 


2211  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  123 


PLATE  XIV 


124  ILUNOIS  BIOLOGICAL  MONOGRAPHS  [222 


EXPLANATION  OF  PLATE 

Fig.  42.  Salt  Fork  canal  looking  east  from  Cottonwood's  road  bridge.  Note  bare  patches 
of  bottom.  September  14, 1920. 

Fig.  43.  Salt  Fork  canal  looking  southeast  from  last  north  and  south  road  bridge. 
September  24, 1920. 

Fig.  44.  Salt  Fork  canal  looking  west  from  last  farmer's  bridge  above  St.  Joseph.  Sep- 
tember 24, 1920.  , 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER 


FAUNA  OF  BIG  VERMILION  RIVER      PLATE  XIV 


2231  FAUNA  OF  BIG  VERMILION  RIVER— BAKER  125 


PLATE  XV 


126  ILLINOIS  BIOLOGICAL  MONOGRAPHS  [224 


EXPLANATION  OF  PLATE 

Fig.  45.    Salt  Fork  canal  looking  south  from  last  east  and  west  road  bridge  west  of 
St.  Joseph.    September  28,  1918. 


ILLINOIS  BIOLOGICAL  MONOGRAPHS 


VOLUME  VII 


BAKER  FAUNA  OF  BIG  VERMILION  RIVER        PLATE  XV 


